51 string interview questions (coding problems with solutions)

String interview questions

String questions come up frequently in coding interviews and you'll need to understand them thoroughly if you want to land a software engineering job. 

Here's a quick list of string interview questions to get started with: 

  • Given a string, create a new string without vowels and print that string.
  • Given a string, create a new string with the same characters in a random order.
  • Given a string containing some words in (possibly nested) parentheses, calculate if all parentheses match.
  • Find the longest common prefix of two given strings.
  • Given two strings, find the shortest edit distance to transform the first into the second.

Below, we have a much more extensive list of questions, including links to high quality solutions for each question.  

And if you need a refresher on string basics, we also have a tutorial and cheat sheet towards the end of this guide. 

Now let's get to the questions!  

  • Easy string interview questions
  • Medium string interview questions
  • Hard string interview questions
  • String basics
  • String cheat sheet
  • Mock interviews for software engineers

Click here to practice coding interviews with ex-FAANG interviewers

1. easy string interview questions.

You might be tempted to try to read all of the possible questions and memorize the solutions, but this is not feasible. Interviewers will always try to find new questions, or ones that are not available online. Instead, you should use these questions to practice the fundamental concepts of strings.

As you consider each question, try to replicate the conditions you’ll encounter in your interview. Begin by writing your own solution without external resources in a fixed amount of time.

If you get stuck, go ahead and look at the solutions, but then try the next one alone again. Don’t get stuck in a loop of reading as many solutions as possible! We’ve analyzed dozens of questions and selected ones that are commonly asked and have clear and high quality answers.

Here are some of the easiest questions you might get asked in a coding interview. These questions are often asked during the ‘phone screen’ stage, so you should be comfortable answering them without being able to write code or use a whiteboard.

1.1 Remove Vowels from a String 

  • Text guide (GeeksforGeeks)
  • Video guide (Kevin Naughton Jr.)

1.2 Defanging an IP Address

  • Code example (LeetCode)

1.3 Jewels and Stones

  • Text guide (Memogrocery)

1.4 Shuffle String

  • Text guide (Medium/RKP)
  • Video guide (Knowledge Mavens)

1.5 Split a String in Balanced Strings

  • Text guide (GeeksForGeeks)

1.6 To Lower Case

  • Text guide (Dev.to/Seanpgallivan)
  • Video guide (Nick White)

1.7 Unique Morse Code Words

1.8 count substrings with only one distinct letter.

  • Text guide (HelloACM)
  • Video guide (GeeksForGeeks)

1.9 Robot Return to Origin

  • Text guide (LeetCode)

1.10 Fizz Buzz

  • Text guide (ITNext/Kevin)
  • Video guide (Tom Scott)

1.11 First Unique Character in a String

  • Text guide (AfterAcademy)

1.12 Reverse String

1.13 valid anagram.

  • Video guide (Terrible Whiteboard)

1.14 Valid Palindrome

  • Text guide (Medium/Urfan)

1.15 Implement Strstr()

  • Text guide (RedQuark)
  • Video guide (Amell Peralta)

1.16 Valid Parentheses

  • Video guide (Back to Back SWE)

1.17 Roman to Integer

  • Video guide (Thecodingworld)

1.18 Longest Common Prefix

1.19 excel sheet column number.

  • Video guide (Knowledge Center)

1.20 Palindrome Permutation

2. medium string interview questions.

Here are some moderate-level questions that are often asked in a video call or onsite interview. You should be prepared to write code or sketch out the solutions on a whiteboard if asked.

2.1 Longest Substring Without Repeating Characters

  • Text guide (Medium/Nerd For Tech)
  • Video guide (Michael Muinos)

2.2 Longest Palindromic Substring

  • Video guide (NeetCode)
  • Video guide (Errichto)

2.3 String to Integer (atoi)

  • Text guide (Medium/Hary) 
  • Video guide (TECH DOSE)

2.4 Letter Combinations of a Phone Number

  • Text guide (Dev.to/Seanpgallivan) 

2.5 Generate Parentheses

  • Text guide (RedQuark) 

2.6 Count and Say

  • Text guide (GeeksforGeeks) 

2.7 Group Anagrams

  • Text guide (Techie Delight) 

2.8 Decode Ways

  • Text guide (Toronto CS) 
  • Video guide (CS Dojo)

2.9 Palindrome Partitioning

2.10 word break.

  • Text guide (ProgrammerSought) 
  • Video guide (Happygirlzt)

2.11 Fraction to Recurring Decimal

2.12 largest number.

  • Text guide (Easy Explanations) 
  • Video guide (Jayati Tiwari)

2.13 Implement Trie (Prefix Tree)

  • Text guide (Medium/Saurav) 

2.14 Basic Calculator II

  • Text guide (Medium/Calvin) 

2.15 Longest Substring with At Least K Repeating Characters

2.16 palindrome partitioning.

  • Text guide (LeetCode) 
  • Video guide (BacktoBackSWE)

2.17 Reorganize String

2.18 zigzag conversion.

  • Video guide (Google Engineer Explains)

2.19 Decode String

  • Text guide (Medium/Signal Cat)

2.20 Multiply Strings

  • Text guide (Medium/Nikhil Anand)

3. Hard string interview questions

Similar to the medium section, these more difficult questions may be asked in an onsite or video call interview. You will likely be given more time if you are expected to create a full solution.

3.1 Regular Expression Matching

  • Video guide (NeetCode) 

3.2 Wildcard Matching

  • Text guide (Techie Delight)
  • Video guide (Tushar Roy) 

3.3 Minimum Window Substring

  • Text guide (Medium/Algo Shaft)
  • Video guide (Back to Back SWE) 

3.4 Word Ladder

  • Video guide (Nick White) 

3.5 Word Break II

  • Text guide (Educative)
  • Video guide (Babybear4812) 

3.6 Word Search II 

  • Text guide (Medium/Hary)
  • Video guide (Timothy H Chang) 

3.7 Serialize and Deserialize Binary Tree

  • Text guide (Dev.to/Akhilpolke)
  • Video guide (BacktoBack SWE) 

3.8 Longest Valid Parentheses

  • Video guide (Algorithms Made Easy) 

3.9 Edit Distance

3.10 alien dictionary (string/graph).

  • Text guide (Medium/Timothy)
  • Video guide (Happygirlzt) 

3.11 Design Search Autocomplete System

  • Code example (Cheonhyangzhang)

4. String basics

In order to crack the questions above and others like them, you’ll need to have a strong understanding of strings and how they work. Let’s get into it.

4.1 What is a string?

A string is an ordered sequence, or string, of characters. It is usually considered a data type and is often included as part of language primitives. In most languages, strings are implemented using an array of bytes. The bytes are encoded using some character encoding. Earlier systems used ASCII encoding, with Unicode encoding used in later systems.

4.1.1 Types of strings (Java, Python, C++)

C++ provides a mutable string, meaning the string contents can be changed after creation.

Python and Java provide an immutable string type. Immutable strings require a new string to be created if any changes are made. This has performance implications for string concatenation when joining a number of strings, running in quadratic time.

Java provides a mutable StringBuilder class, which should be used for concatenating multiple strings. In Python, generally the `.join` method on strings should be used, which accepts an iterable of multiple strings. Using Java's StringBuilder or Python’s `.join` provides a linear time solution for multiple string concatenations. 

Another class of strings are C-style strings, so named as they are used in the C language. These strings are simple arrays. A special terminating character is stored directly after the last character of the string. This terminating character marks the end of the string within the array, or buffer. C++ has support for C-style strings, but it is preferable to use C++ style strings in pure C++ code.

Java, Python and C++ strings are more complex data structures, with class or struct methods for manipulating and querying them.

4.1.2 How strings store data

There are generally two types of string implementations: null-terminated strings (C strings), and non-null-terminated strings. The principal difference between these types of strings is how the termination and tracking the length of the string is handled. 

Null-terminated strings (C strings) are character arrays terminated with a null (NUL) character, typically a byte with all bits set to 0. The length of the string is calculated by counting the characters in the string up to the terminating character. Care must be taken in working with C-style strings, as writing and reading past the end of the string terminator can result in buffer overflow errors, causing unexpected behaviour and security issues by overwriting or reading unrelated memory contents.

Non-null-terminated strings, as used in C++, Java and Python implementations, have the underlying array and the length stored separately. In Java this is a class with private fields for the character array and length, which are not directly accessible from outside the class. 

C++, Java and Python strings have useful class and instance methods to work with strings. Commonly used are: 

  • Substring queries to return a new string from a subset of the original string
  • Replace methods to return a new string with a specific sequence of character substituted for another
  • String formatters to create strings from a template and data variables
  • Trimming methods to create new strings without leading or trailing whitespace
  • Upper and lower case conversion methods
  • Methods to check if a string contains a given substring 

For more advanced pattern matching in strings, Regular Expressions, or regexes, are commonly used. Most modern string implementations have support for regex queries.

4.1.3 Deep dive into tries

A trie, or prefix tree, is a type of search tree, often used with strings. The strangely spelt name is from "reTrieval," but is mostly pronounced as "try." Tries are useful for answering questions like, "Given an input sequence 'cod,' what possible words could be formed?" This makes tries useful for auto-completing words in text input in a range of use cases, including search and texting . 

A trie data structure is made of nodes indexed with a single character key. Each node has references to its child nodes. The number of child nodes is bounded by the number of unique characters in the alphabet space making up the stored words. Often this is described as 26 for the English language, but it can be larger when taking into consideration accented characters, or if there are numeric and special characters in the alphabet space. Each node also has a flag signaling the end of a word, represented by a blue node below:

Strings explanation

Since each node only contains one character, the complete key to that node is distributed from its parents down to that node. Retrieval of a key is a depth-first search of the trie. A search for a key ends when the end of the word node is reached. Inserting a new key is done by following the trie through each character of the new key, and adding each character as a trie node where needed, and marking the node of the last character as the end of the word. 

Inserting and searching is O(keySize) time. Space requirements are much larger than a simple string though, at O(AlphabetSpace*keySize*n), n being the total number of keys in the trie.

5. Strings cheat sheet

String definition: A string is a sequence of characters, often implemented as an array.

String interview questions cheat sheet

You can download this cheat sheet here.

5.1 Related algorithms and techniques

  • State Machines  
  • String Builder
  • Two pointers
  • Backtracking
  • Levenshtein Distance
  • Boyer-Moore string search algorithm
  • Knuth-Morris-Pratt Algorithm
  • Rubin-Karp Algorithm
  • Bitap algorithm
  • BW Data transform

5.2 Cheat sheet explained

The cheat sheet above is a summary of information you might need to know for an interview, but it’s usually not enough to simply memorize it. Instead, aim to understand each result so that you can give the answer in context.

The cheat sheet is broken into time complexity (the processing time for the various string operations) and space complexity (the amount of memory required). While you might be asked about these directly in relation to string data structures, it’s more likely that you will need to know these in relation to specific string-related algorithms, such as substring searching, which is what the second section of the cheat sheet details.

For more information about time and space requirements of different algorithms, read our  complete guide to big-O notation and complexity analysis .

5.2.1 Time complexity

Accessing a character at a particular index in a string is an O(1) operation, as strings are stored as arrays. Deleting characters from immutable strings means creating a new string and copying the remaining characters over, so this is an O(n) operation. For mutable strings, it means removing characters and shifting remaining characters, which is also O(n). Inserting into a string is a similar level of work as deleting, again O(n) time for both mutable and immutable strings.

Searching for a substring using built-in methods in most languages is generally O(n*m), depending on the algorithm used. We explain this more in the algorithm section.

Slicing, or splitting, a string refers to creating multiple substrings by splitting a string on a character or character sequence. This is often used in parsing CSV type files. It runs in O(n) time, as each character needs to be copied out into the new strings. 

Joining, or concatenating, strings is a more complex operation. For immutable strings, concatenating multiple strings can result in O(n 2 ) time complexity for large numbers of strings. In such cases, StringBuilder, or Python's '.join()' method is recommended. For concating two mutable strings, it is O(n+m), where n and m represent the number of characters in either string. Mutable strings can concatenate faster, depending on the underlying implementation. For implementations where the array is doubled in size each time a resizing is needed, string concatenation is closer to regular array time complexity.

Comparing strings is also O(n) time, as generally each character needs to be checked. 

For tries, there are two significant operations: Inserting a new key, and retrieving (searching for) a key. Both run in O(m) time, where m is the size of the key. This makes tries very scalable, as the time complexity is not dependent on the size of the trie itself.

5.2.2 String algorithm complexity

Radix sort is usually shown in the context of sorting numbers, but it can be used to sort strings, if the buckets are indexed by characters rather than numbers. Essentially the alphabet space of the strings becomes the base as used by the radix sort algorithm.

Many string algorithms center around searching for all occurrences of a substring within a string. This is a fundamental operation in text-centered applications, from HTTP processing to word processing. The naive implementation slides the search pattern by one character over the length of the string to check for the pattern starting at each index. This makes it an O(m*(n-m+1)) operation, as the pattern needs to be checked at each character in the string. The more sophisticated algorithms in the list attempt to reduce this complexity. These algorithms reduce the time by using strategies such as precomputing tables, creating rolling hashes, and using caching state from previous matching. They also use the fact that useful information for shortcutting the naive search approach is available in the search pattern itself, for example, whether or not the search pattern has repeating characters can allow some sliding indexes to be skipped. In all, these algorithms provide ways to reduce searching to O(n) time complexity.

6. Mock interviews for software engineers

Before you start practicing interviews, you’ll want to make sure you have a strong understanding of not only linked lists but also the rest of the relevant data structures. Check out our guides for questions, explanations and helpful cheat sheets.

  • Linked lists
  • Stacks and Queues
  • Coding interview examples (with solutions)

Once you’re confident on all of the data structure topics, you’ll want to start practicing answering coding questions in an interview situation. One way of doing this is by practicing out loud, which is a very underrated way of preparing. However, sooner or later you’re probably going to want some expert interventions and feedback to really improve your interview skills.

That’s why we recommend practicing with ex-interviewers from top tech companies. If you know a software engineer who has experience running interviews at a big tech company, then that's fantastic. But for most of us, it's tough to find the right connections to make this happen. And it might also be difficult to practice multiple hours with that person unless you know them really well.

Here's the good news. We've already made the connections for you. We’ve created a coaching service where you can practice system design interviews 1-on-1 with ex-interviewers from leading tech companies. Learn more and start scheduling sessions today.

Interview coach and candidate conduct a video call

InterviewPrep

Top 25 String Manipulation Interview Questions and Answers

Prepare for your next coding interview with our comprehensive guide on string manipulation. Discover common questions, insightful answers, and practical examples to enhance your coding skills.

string interview questions problem solving

String manipulation, a fundamental aspect of any programming language, involves the ability to modify and interact with strings – sequences of characters that include letters, numbers, symbols, or spaces. The importance of string manipulation cannot be overstated as it is used in various applications such as data cleaning, pattern recognition, parsing, and so much more.

Regardless of whether you’re working in Python, Java, C++, JavaScript, or any other language, understanding how to effectively manipulate strings is an essential skill for every developer. It’s also a common area of inquiry during technical interviews, given its ubiquity in coding challenges and real-world problem-solving scenarios.

In this article, we delve into a comprehensive collection of interview questions focused on string manipulation. These questions are designed to test your knowledge about different methods of manipulating strings, finding patterns, comparing, searching, and even converting strings. Whether you’re a beginner just starting out or a seasoned programmer looking to refresh your skills, these questions will provide invaluable insights into handling one of the most commonly used data types in programming.

1. Can you explain what String Manipulation is and why it’s important in software development?

String manipulation refers to the process of handling and modifying strings, a sequence of characters, in programming. It’s crucial in software development for several reasons.

Firstly, it aids in data cleaning by removing unnecessary spaces or converting case types, enhancing data consistency. Secondly, it enables parsing where strings are broken into smaller parts for easier analysis. This is vital when dealing with large volumes of text data. Thirdly, string manipulation allows for effective communication between different systems through formatting strings to meet specific system requirements.

Moreover, it facilitates user-friendly outputs. By manipulating strings, developers can format information in a way that’s easy for users to understand. Lastly, it supports pattern matching and searching within strings, which is essential in many applications like search engines.

2. Can you describe how to reverse a string using an iterative approach in Python?

In Python, reversing a string using an iterative approach involves creating a new empty string and then appending each character from the original string to it in reverse order. This can be achieved by initializing an empty string, then iterating over the length of the original string starting from the last index (which is -1 in Python) and moving towards the first index (0). For each iteration, we append the current character to our new string. Here’s a simple code example:

This function takes an input string, iterates over it in reverse order, and appends each character to reversed_str . The result is a reversed version of the original string.

3. How would you remove all white spaces from a string without using the replace() method?

To remove all white spaces from a string without using the replace() method, we can use the split() and join() methods. The split() method splits a string into an array of substrings based on a specified delimiter, in this case, a space character. This effectively removes all spaces from the string. However, it leaves us with an array of substrings rather than a single string. To convert this back into a single string, we use the join() method which concatenates all elements of an array into a single string.

Here is a JavaScript example:

In this code snippet, ‘str’ initially contains a string with spaces. We then call the split() method on ‘str’, passing in a space character as the argument. This splits ‘str’ into an array of words. We immediately call join() on this array, passing in an empty string as the argument. This joins all the words together into a single string with no spaces.

4. What algorithms would you use to check if a string is a palindrome?

To check if a string is a palindrome, two algorithms can be used: the Two-Pointer Technique and the Stack Method.

The Two-Pointer Technique involves initializing two pointers at both ends of the string. The characters at these pointer positions are compared. If they match, the pointers move towards each other until they meet in the middle or cross paths. If all character comparisons match, the string is a palindrome.

The Stack Method uses a stack data structure to store half the string’s characters. It then pops off each character from the stack and compares it with the remaining half of the string. A matching sequence indicates a palindrome.

5. How would you go about finding the duplicate characters in a string?

To find duplicate characters in a string, I would use a hash map data structure. The key-value pair of the hash map would be character-frequency pairs. First, iterate through each character in the string and add it to the hash map with its frequency count. If a character is already present in the hash map, increment its frequency by one. After iterating through all characters, traverse the hash map. Any character with a frequency greater than one is a duplicate.

6. Can you explain the concept of string immutability? What are its implications in programming?

String immutability refers to the property of strings that prevents their modification once created. In programming languages like Python and Java, strings are immutable objects. This means when you try to update the value of an immutable string, a new object is created instead of modifying the original one.

The implications of string immutability in programming are significant. It enhances performance by allowing strings to be reused without creating additional copies. This saves memory space and improves efficiency. However, it can also lead to increased processing time if large numbers of strings need to be concatenated or manipulated, as each operation results in a new string object.

Immutable strings also contribute to safer code. Since they cannot be changed after creation, they can be used as keys in dictionaries or elements in sets without fear of unexpected changes. Moreover, they help maintain thread safety in multi-threaded environments because they eliminate the risk of data corruption due to simultaneous modifications from different threads.

7. How would you implement a case-insensitive string comparison function?

To implement a case-insensitive string comparison function, we can use the built-in functions provided by most programming languages. For instance, in Python, we would convert both strings to lower or upper case using the .lower() or .upper() methods respectively before comparing them.

Here’s an example:

In this code snippet, str1 and str2 are the two input strings. The .lower() method is called on each string to convert all characters to lowercase. Then, the equality operator ( == ) compares these modified strings. If they match, the function returns True; otherwise, it returns False.

8. In JavaScript, how would you convert a string to a number and vice versa?

In JavaScript, to convert a string to a number, you can use the Number() function or the parseInt() and parseFloat() functions. The Number() function converts the entire string while parseInt() and parseFloat() stop at the first non-numeric character.

Example: let str = “123”; let num = Number(str); // 123

For converting a number to a string, we use the toString() method. This method returns a string representing the specified number object.

Example: let num = 123; let str = num.toString(); // “123”

9. How would you check if two strings are anagrams of each other in a highly efficient way?

An efficient way to check if two strings are anagrams is by using a frequency count method. This involves creating a character array of size 26 for each string, representing the English alphabet. Each index in the array corresponds to a letter and its value represents the frequency of that letter in the string.

Firstly, initialize both arrays with zeros. Then iterate through each character in the first string, incrementing the corresponding index in the first array. Repeat this process for the second string but decrement the corresponding index in the second array.

Finally, compare the two arrays. If they’re identical, the strings are anagrams. Otherwise, they’re not. The time complexity of this approach is O(n), where n is the length of the strings.

10. Can you describe how you would find all permutations of a string?

To find all permutations of a string, we can use recursion. We start by fixing the first character and recursively generating permutations for the remaining characters. Once this is done, we swap the first character with the next one and repeat the process until we’ve swapped with every character in the string. This will generate all possible permutations as each position in the string is occupied by every character exactly once.

For example, consider the string “ABC”. Initially, ‘A’ is fixed and permutations are generated for ‘BC’. Then ‘B’ is swapped with ‘A’, so now ‘B’ is fixed and permutations are generated for ‘AC’. Finally, ‘C’ is swapped with ‘A’, so ‘C’ is fixed and permutations are generated for ‘AB’.

This method ensures that all permutations are found without repetition. However, it’s important to note that this approach has a time complexity of O(n*n!) due to the n! permutations and n recursive calls for each permutation.

11. How would you reverse words in a given sentence without using any library method?

To reverse words in a sentence without using any library method, we can follow these steps:

1. Convert the sentence into an array of words by splitting it at spaces. 2. Initialize an empty string to hold the reversed sentence. 3. Iterate over the word array from end to start. 4. For each iteration, append the current word and a space to the reversed sentence. 5. After the loop ends, remove the trailing space from the reversed sentence.

Here is a Python code example:

12. What methods would you use to find the length of a string without using the len() function?

To find the length of a string without using len(), we can use two methods. The first method is to use a for loop. Initialize a counter variable at zero, then iterate over each character in the string, incrementing the counter by one each time. At the end of the loop, the counter will hold the length of the string.

The second method involves using the reduce function from the functools module. This function applies a binary function (a function that takes two arguments) to all items in an iterable in a cumulative way. We can pass a lambda function that increments a counter for each character in the string and the string itself as the iterable.

Here’s how it looks in code:

13. Can you demonstrate how to count the occurrence of a given character in a string?

Yes, I can demonstrate this using Python. The built-in count() function is used to count the occurrence of a character in a string.

In this code, we define a function called char_count that takes two parameters: a string and a character. Inside the function, we use the count() method on the string to count the number of times the character appears. We then call this function with a test string and character, and print the result.

14. How would you convert a string to a character array in Java?

In Java, a string can be converted to a character array using the built-in method “toCharArray()”. This method is part of the String class and returns an array containing each character in the original string. Here’s how it works:

In this code snippet, we first declare a string ‘str’ with the value “Example”. Then, we call the “toCharArray()” method on ‘str’, which converts it into a character array ‘charArray’. Now, ‘charArray’ contains the individual characters of “Example”.

15. Can you explain the differences between a string and a string buffer?

A string is an immutable object in Java, meaning once it’s created, its state cannot be changed. Any modification to a String results in a new instance, leading to memory inefficiency if many modifications are made.

On the other hand, StringBuffer is mutable. Modifications like append or insert can be made without creating a new instance. This makes StringBuffer more efficient when performing repeated operations on strings.

Another difference lies in synchronization. StringBuffer methods are synchronized, making them thread-safe and suitable for multi-threading environments. In contrast, String is not thread-safe.

16. How would you implement multi-line strings in Python and Java?

In Python, multi-line strings are implemented using triple quotes. You can use either three single quotes (”’) or three double quotes (“””). For example:

Java doesn’t directly support multi-line strings. However, you can achieve this by concatenating strings with the ‘+’ operator and including newline characters (‘\n’). Alternatively, since Java 13, you can use text blocks which are enclosed in triple double quotes (“””…”””). Here’s an example:

18. Can you explain how string concatenation works in JavaScript?

In JavaScript, string concatenation is the process of joining two or more strings together. This can be achieved using the ‘+’ operator or the ‘concat()’ method.

The ‘+’ operator merges two strings into one. For example, let’s consider two strings: var str1 = “Hello”; var str2 = “World”. The concatenated string would be: var result = str1 + ” ” + str2; //result is “Hello World”.

Alternatively, the ‘concat()’ method can also be used for string concatenation. It combines the text from two (or more) strings and returns a new string. Using our previous variables, we could write: var result = str1.concat(” “, str2); //result is “Hello World”.

It’s important to note that neither the ‘+’ operator nor the ‘concat()’ method modify the original strings. They both return a new string which is the result of the concatenation.

19. How would you find the longest palindrome in a given string?

To find the longest palindrome in a string, we can use dynamic programming. We initialize a 2D array of size n*n (where n is the length of the string) to false. Each cell [i][j] represents whether the substring from index i to j is a palindrome.

We then iterate over the string in reverse order. For each character, we check all substrings that end with this character. If the substring is a palindrome, we update our answer.

The pseudocode for this algorithm would be:

20. Can you write a function to check if a string is a substring of another string without using any built-in functions?

Yes, a function can be written to check if a string is a substring of another without using built-in functions. Here’s an example in Python:

This function iterates over the main string and checks each character against the corresponding character in the potential substring. If all characters match, it returns True; otherwise, it continues checking until it has exhausted all possibilities or found a match.

21. How would you count the number of vowels and consonants in a string?

To count the number of vowels and consonants in a string, we can use an iterative approach. First, initialize two counters to zero: one for vowels and another for consonants. Then, iterate over each character in the string. If the character is a vowel (a, e, i, o, u), increment the vowel counter. If it’s a letter but not a vowel, increment the consonant counter. Here’s a Python example:

This function converts the input string to lowercase, then iterates through each character. It checks whether the character is a letter and if so, whether it’s a vowel or a consonant, updating the respective counters accordingly.

22. Can you explain the role of escape sequences in string manipulation?

Escape sequences play a crucial role in string manipulation by allowing the inclusion of special characters within strings that cannot be typed directly. They are denoted by a backslash (\) followed by a letter or combination of digits. For instance, “\n” is used for a new line, “\t” for a tab, and “\\” to include a literal backslash. Escape sequences also enable the use of non-printable ASCII control characters like “\0″ (null character). In coding languages such as Python, escape sequences can be used with both single (‘ ‘) and double (” “) quotes to prevent them from being interpreted as the end of a string.

23. How would you find the first non-repeating character in a string?

To find the first non-repeating character in a string, we can use a hash map. The keys of this map are characters from the input string and values are their counts. We iterate through the string, for each character, if it’s not already in the map, add it with count 1; if it is, increment its count. After that, iterate again over the string, checking each character’s count in the map. The first character with a count of 1 is our answer.

Here’s an example in Python:

24. How do you split a string into a list of words in Python?

In Python, the split() method is used to divide a string into a list of words. This function splits the string at each instance of white space by default. Here’s an example:

This code will output: [‘Hello’, ‘World’]

If you want to split on something other than whitespace, you can pass that as an argument to the split() function. For example:

This code will output: [‘apple’, ‘banana’, ‘cherry’]

25. Can you describe the difference in memory allocation between a string and a string builder in .NET?

In .NET, strings are immutable objects. This means once a string is created, it cannot be changed. Any operation that appears to modify the string actually creates a new one in memory. This can lead to inefficient use of resources when performing multiple modifications on a string.

On the other hand, StringBuilder is mutable. It allows for efficient manipulation of large or complex strings as it doesn’t create a new object in memory with each modification. Instead, it modifies the existing object, reducing memory usage and improving performance.

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Top 21 String Programming and Coding Interview Questions With Solutions

String programming and coding interview questions.

21 String Coding Problems from Java Interviews

  • 75+ Coding Problems from Interviews ( questions )
  • 10 Free Courses to learn Data Structure and Algorithms ( courses )
  • 10 Books to Prepare Technical Programming/Coding Job Interviews ( books )
  • 10 Courses to Prepare for Programming Job Interviews ( courses )
  • 100+ Data Structure and Algorithms Interview Questions ( questions )
  • My favorite Free Algorithms and Data Structure Courses on FreeCodeCamp ( courses )
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  • 10 Coding Tips and 101 Coding Questions for Interviews ( tips )
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  • 5 Free Courses to learn Algorithms in-depth ( courses )
  • 10 Algorithms books every Programmer should read ( books )
  • Top 5 Data Structure and Algorithms Courses for Programmers ( courses )

Javin Paul

About Author

Javin Paul is a Java Programmer, blogger and author. Javin has more than 18 years of software development experience working on server-side Java technologies, multithreading, concurrency, FIX Protocol etc. He has a passion for teaching and authored books like Grokking the Java Interview and Grokking the Spring Boot Interview.

10 comments:

Hi guys, here the first question is "How to find the maximum occurring character in given String?" but the solution link is for "How to Count Occurrences of a Character in String" Both are different, Please confirm...

string interview questions problem solving

Yes, you are right but once you know how to count character then the other one becomes simple because you just need to return the character with maximum count

boolean b=true;

yes both are different example 1)How to find the maximum occurring character in given String?" Malyalaum - a-3 (a is the maximum occurring character in given string) 2) How to Count Occurrences of a Character in String Malyalaum m-2 a-3 y-1 u-1 thank you,

That's correct but once you know how to count character then the other one becomes simple because you just need to return the character with maximum count

public class OccObj { public static void main(String[] args){ Scanner input=new Scanner(System.in); String s= input.next(); NoOfOcuu(s); } public static void NoOfOcuu(String s){ int c=0,c2=0; ArrayListn=new ArrayList<>(); char c1='0'; for(int i=0;i=i)&&(c2==0)) { if (s.charAt(i) == s.charAt(j)) { c++; } } } if(c>1){ n.add(s.charAt(i)); } if(c>0) { System.out.println("the vale:" + s.charAt(i) + " - " + c); } } } }

public static void NoOfOcuu(String s){ int c=0,c2=0; ArrayListn=new ArrayList<>(); char c1='0'; for(int i=0;i=i)&&(c2==0)) { if (s.charAt(i) == s.charAt(j)) { c++; } } } if(c>1){ n.add(s.charAt(i)); } if(c>0) { System.out.println("the vale:" + s.charAt(i) + " - " + c); } } }

19)function isPalindrome(str) { let emptyArr = []; for (let i = 0; i < str.length; i++) { let x = str[i]; if (x == "(" || x == "[" || x == "{") { emptyArr.push(x); continue; } if (emptyArr.length == 0) return false; let y; switch (x) { case ")": y = emptyArr.pop(); if (y == "{" || y == "[") return false; break; case "}": y = emptyArr.pop(); if (y == "(" || y == "[") return false; break; case "]": y = emptyArr.pop(); if (y == "(" || y == "{") return false; break; } } return emptyArr.length == 0; } if (isPalindrome("{}")) console.log(true); else console.log(false);

val str = "aabbbbaa" var l = str.length var s = "" while (l>0){ s = s + str.get(l-1) l-- } if(s.equals(str)) { println("palindrome string : " + s) }else{ println("No palindrome string : " + s) }

Hi guys, here is the solution for question number 4 "How to remove characters from the first String which are present in the second String?" public static void main(String[] args) { String st1 = "india is great"; String st2 = "in"; List secondStringList = st2.chars().mapToObj(c -> (char) c).collect(Collectors.toList()); String outputString = st1.chars().mapToObj(c -> (char) c).filter(c -> !secondStringList.contains(c)).map(ch -> new String(String.valueOf(ch))) .collect(Collectors.joining("")); System.out.println("outputString : " + outputString); }

Feel free to comment, ask questions if you have any doubt.

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Posted on Jun 1, 2019 • Updated on Jan 10, 2021

Top 20 String Coding Problems from Programming Job Interviews

Disclosure: This post includes affiliate links; I may receive compensation if you purchase products or services from the different links provided in this article.

string interview questions problem solving

This is very obvious because I have also never written a program where I have not used a single String variable. You will always find String as one of the most used data type or data structure in any program.

In this article, I am going to share some of the most common String based coding problems I have come across from many Programming interviews I have been part of. I also have experience from both sides of the table as a candidate as well as an Interviewer so I know how important these questions are.

Btw, there is no point in solving these questions if you don't have basic knowledge of data structure or you have not to refresh them in recent times. In that case, I suggest you first go through a good data structure and algorithm course or book to revise the concept.

This will save you a lot of time going back and forth between the book and your IDE for each question.

If you need resources, I suggest following online courses to learn Data structure and Algorithms , even though they are independent of any programming language, I strongly suggest you join the course which explains problems in the programming language you are most comfortable with.

  • Data Structures and Algorithms: Deep Dive Using Java for Java developers
  • Algorithms and Data Structures in Python for those who love Python
  • JavaScript Algorithms and Data Structures Masterclass by Colt Steele for JavaScript programmers
  • Mastering Data Structures & Algorithms using C and C++ for those who are good at C/C++

How to solve String based Coding Problems?

A good thing about the string data structure is that if you know the array data structure, you can easily solve string-based problems because strings are nothing but a character array .

So all the techniques you know by solving array-based coding questions can be used to solve string programming questions as well.

Here is my list of some of the frequently asked string coding questions from programming job interviews:

  • How do you reverse a given string in place? ( solution )
  • How do you print duplicate characters from a string? ( solution )
  • How do you check if two strings are anagrams of each other? ( solution )
  • How do you find all the permutations of a string? ( solution )
  • How can a given string be reversed using recursion? ( solution )
  • How do you check if a string contains only digits? ( solution )
  • How do you find duplicate characters in a given string? ( solution )
  • How do you count the number of vowels and consonants in a given string? ( solution )
  • How do you count the occurrence of a given character in a string? ( solution )
  • How do you print the first non-repeated character from a string? ( solution )
  • How do you convert a given String into int like the atoi() ? ( solution )
  • How do you reverse words in a given sentence without using any library method? ( solution )
  • How do you check if two strings are a rotation of each other? ( solution )
  • How do you check if a given string is a palindrome? ( solution )
  • How do you find the length of the longest substring without repeating characters? (solution)
  • Given string str, How do you find the longest palindromic substring in str? (solution)
  • How to convert a byte array to String? ( solution )
  • how to remove the duplicate character from String? ( solution )
  • How to find the maximum occurring character in a given String? ( solution )
  • How do you remove a given character from String? ( solution )

These questions help improve your knowledge of string as a data structure.

If you can solve all these String questions without any help then you are in good shape.

For more advanced questions, I suggest you solve problems given in the Algorithm Design Manual by Steven Skiena , a book with the toughest algorithm questions.

string interview questions problem solving

If you need to revise your Data Structure and Algorithms concepts then you can also see these resources:

1. Data Structures and Algorithms: Deep Dive Using Java for Java developers

2. Algorithms and Data Structures in Python for those who love Python

3. JavaScript Algorithms and Data Structures Masterclass by Colt Steele for JavaScript programmers

4. Mastering Data Structures & Algorithms using C and C++ for those who are good at C/C++

These are some of the best courses on data structures and algorithms and you can choose the one which is most suitable for you. Btw, I will receive payments if you buy these courses

Now You're Ready for the Coding Interview

These are some of the most common questions outside of data structure and algorithms that help you to do really well in your interview.

I have also shared a lot of these questions on my javarevisited and java67 , so if you are really interested, you can always go there and search for them.

These common String based questions are the ones you need to know to successfully interview with any company, big or small, for any level of programming job.

If you are looking for a programming or software development job in 2018, you can start your preparation with this list of coding questions but you need to prepare other topics as well.

This list of 50+ data structure and algorithms problems provides good topics to prepare and also helps assess your preparation to find out your areas of strength and weakness.

Good knowledge of data structure and algorithms is important for success in coding interviews and that's where you should focus most of your attention.

Further Learning 10 Algorithm Books Every Programmer Should Read Top 5 Data Structure and Algorithm Books for Java Developers From 0 to 1: Data Structures & Algorithms in Java Data Structure and Algorithms Analysis --- Job Interview 50+ Data Structure and Coding Problems for Programmers 10 Data Structure, Algorithms and SQL Courses to Crack Coding Interviews 20+ Array Coding Problems for Programmers 20+ Linked List Coding Problems for Programmers 25+ System Design Coding Problems for interviews

Closing Notes

Thanks, You made it to the end of the article ... Good luck with your programming interview! It's certainly not going to be easy, but you are one step closer after practicing these questions.

If you like this article, then please share it with your friends and colleagues, and don't forget to follow javinpaul on Twitter!

P.S. --- If you need some FREE resources for Programming Job Interviews, you can check out this list of free data structure and algorithm courses to start your preparation.

Top comments (18)

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beachbc profile image

  • Location Portland, OR
  • Work Senior Fullstack Developer at Oregon Public Broadcasting
  • Joined Jun 2, 2019

"Thank you for selecting me as a candidate to interview, if you honestly think I've worked my way up to being a senior developer without knowing how to actually perform the job, then this isn't an organization I want to work for. I'm sure we both have more important things to do with our time, so why don't we go ahead and end this now."

  • Joined Sep 16, 2018

Well @Bradley, I do understand that after a certain level of experience you may find it offending solving these questions but that's not the goal. If you are hands-on with coding, you can easily solve these problems but if you struggle with solving these, it means you are a bit rusty and not really doing coding everyday.

It doesn't matter to me how easy the questions are to answer. To me:

The question is trying to verify that I know how to do trivial and/or esoteric operations off the top of my head, which lets be honest, who has ever had to reverse the words of a sentence? Likewise, who hasn't had to strip bad characters out of a string?

The interviewers care about my rote memorization, which has nothing to do with being a good developer.

The company put someone in charge of interviewing that isn't a developer and they pulled questions off the internet thinking this is what makes a great developer.

The person in charge of hiring is too busy or too lazy to put the time into determining if a long list of candidates are a good fit for their organization, so they use this as a quick way to weed out candidates in round one. Mission successful; if they're not going to put the time into selecting quality candidates then right off the bat I'm not too excited about my prospective coworkers, nor the support I can expect from the organization.

What I'm saying is that a company asking this type of question tells me all I need to know about that company.

About the most I'll do is some sort of take home project and discuss at the interview: at least then I can either use a language or library I haven't used in a long time or learn a new one while I'm doing the project so that I'm not wasting my time.

philrod1 profile image

  • Joined Jun 1, 2019

Exactly! Job interviews are a two-way thing. Or at least they should be.

mt3o profile image

  • Joined Aug 15, 2018

Horrible idea for a job interview. Perhaps for a junior position, or even for an internship, but not for a senior, or at least for minimally independent position. All of those problems are easily solvable with Google. On the other hand, as a senior, you have to work with multiple different languages, technologies, paradigms and be able to to figure out best way to solve the problem, having multiple proposed solutions. Problems you referred are trivial, well known and deeply exploited.

From my experience, I had people who excelled at this kind of questions but failed at "as a java developer i won't touch js/html" kind of test. As a scrum master and main developer on the team I cannot accept situation where one of the members can't (don't want to) handle tasks other people do.

As interviewer I like this question: which features of java8+ are most important to you? It gives the interviewee chance to gather thoughts, check if he is up to date and on which parts of the language he focuses. And there is no "bad" answer. All answers reflect how they think, what they focus on, and, honestly, if you rate people's creativity by number of algorithms they memorized, you'll assemble a team of losers who can't solve any problem unless it's already solved by a business analyst.

I don't want to work for you. Sorry.

mia26mba08 profile image

Possibly the worst way to hire someone. They give zero indication of a devs ability.

I don't know why you think so because this is not the only interview anyone will give to get the job. It's not that easy. this is just a part of a big hiring process.

The java example of reversing a string in-place is wrong. Strings are immutable in Java. The example given will involve two array copies.

Well, while you are correct, it's about logic. In reality, it's better to use StringBuilder.reverse() but yes, mentioning that fact can impress some interviewers too.

humbertobeltrao profile image

I think that trying to let things clear during the interview helps the candidate to understand the importance behind these kind of questions. In one of the process I participated the interviewer explained that solving the string problems I was facing was not the point. He explained the time constraints the projects used to demand in the company and for that reason code performance and complexity concerns would be also evaluated. String problems themselves probably do not represent the scenario a candidate will be working on, but perhaps telling about the skills required to not hit the iceberg helps to care about its top.

For comparison, look here: businessinsider.com/how-tech-compa...

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Wednesday, September 20, 2023

Top 20 string algorithm questions from coding interviews, 20 string algorithm based coding interview questions, 1) how to print duplicate characters from string ( solution ), 2) how to check if two strings are anagrams of each other ( solution ), 3) how to program to print first non repeated character from string ( solution ).

Top 20 String Algorithm Questions from Coding Interviews

19) Write a program to find the longest palindrome in a string? (solution)

20) how to sort string on their length in java (solution).

20 String Algorithm Questions from Coding Interviews

Last Updated on October 10, 2023 by Abhishek Sharma

string interview questions problem solving

Java, one of the most popular programming languages, offers a rich set of features and libraries to developers. Among its core components, handling strings is a fundamental and frequently used aspect. Whether you’re a seasoned Java developer or just starting your programming journey, proficiency in working with strings is essential. As you prepare for a Java interview, mastering string manipulation and understanding the nuances of Java’s String class is critical.

This article serves as your comprehensive guide to Java String interview questions. We’ve curated a list of common questions that interviewers often pose to assess a candidate’s expertise in string handling. By exploring these questions and their solutions, you’ll gain a deeper understanding of how to work with strings in Java, making you better prepared to shine in your upcoming Java interview.

Commonly Asked Java String Interview Questions

Certainly! Here are some common Java String interview questions along with their answers:

1. What is the difference between String, StringBuilder, and StringBuffer in Java? Answer: String is immutable, meaning its content cannot be changed once it is created. StringBuilder is mutable and used when you need to perform a lot of string manipulations efficiently. StringBuffer is similar to StringBuilder but is thread-safe, making it suitable for multi-threaded applications.

2. How do you create an empty string in Java? Answer: You can create an empty string using the empty string literal "" or by using the String constructor with no arguments, like this: String emptyString = new String();

3. Explain the equals() method in the String class and how it differs from ==. Answer: The equals() method in the String class checks if the content of two strings is equal. The == operator checks if two string references point to the same memory location (object identity).

4. How can you concatenate strings in Java? Answer: You can concatenate strings using the + operator or by using the concat() method. For example:

5. What is the purpose of the charAt() method in the String class? Answer: The charAt(int index) method returns the character at the specified index in the string. It allows you to access individual characters within a string.

6. Explain how to convert a string to uppercase and lowercase in Java. Answer: You can use the toUpperCase() and toLowerCase() methods to convert a string to uppercase or lowercase, respectively. For example:

7. How do you check if a string contains a specific substring in Java? Answer: You can use the contains() method or the indexOf() method to check if a string contains a substring. For example:

8. What is the purpose of the split() method in Java, and how is it used? Answer: The split() method is used to split a string into an array of substrings based on a specified delimiter. For example:

9. What is the difference between String and StringBuffer when it comes to thread safety? Answer: String is immutable and inherently thread-safe. Once created, its content cannot be modified. In contrast, StringBuffer is mutable and designed to be thread-safe, allowing concurrent modification by multiple threads without synchronization.

10. How do you remove leading and trailing whitespace from a string in Java? Answer: You can use the trim() method to remove leading and trailing whitespace from a string. For example:

11. What is the substring() method in Java, and how is it used? Answer: The substring(int beginIndex) method returns a new string that is a substring of the original string, starting from the beginIndex to the end of the string. You can also use the substring(int beginIndex, int endIndex) method to specify both the starting and ending indices.

12. Explain the concept of string immutability in Java. Answer: String immutability means that once a string is created, its value cannot be changed. Any operation that appears to modify a string actually creates a new string. This property ensures that string references remain constant.

13. How do you compare two strings in Java, considering case sensitivity? Answer: To compare two strings while considering case sensitivity, you can use the equals() method. For case-insensitive comparison, you can use equalsIgnoreCase().

14. What is the purpose of the replace() method in the String class? Answer: The replace(CharSequence target, CharSequence replacement) method replaces all occurrences of the target substring with the replacement substring within the string. It returns a new string with the replacements made.

15. How do you convert an integer or other data types to a string in Java? Answer: You can convert other data types to a string in Java using the String.valueOf() method or by concatenating the value with an empty string. For example:

16. Explain the concept of string pooling in Java. Answer: String pooling, also known as string interning, is a memory optimization technique where Java maintains a pool of unique string literals. When you create a string using double quotes, Java checks the pool to see if an identical string already exists. If it does, the new string references the existing one, reducing memory usage.

17. What is the purpose of the StringBuilder class in Java, and why is it preferred for string concatenation in loops? Answer: StringBuilder is used for efficient string manipulation in cases where the string content may change frequently, such as inside loops. It is preferred over string concatenation using + because it avoids creating a new string object for each concatenation, which can be inefficient in memory and performance.

18. How do you reverse a string in Java? Answer: You can reverse a string in Java by converting it to a StringBuilder, using the reverse() method, and then converting it back to a string. For example:

19. What is an anagram, and how do you check if two strings are anagrams of each other in Java? Answer: An anagram is a word or phrase formed by rearranging the letters of another. To check if two strings are anagrams, you can sort the characters in both strings and compare the sorted strings.

20. How can you count the occurrences of a specific character in a string in Java? Answer: You can count the occurrences of a specific character in a string using a loop or by using the replace() method to remove all occurrences of the character and then subtracting the length of the resulting string from the original string.

21. What is the purpose of the valueOf() method in Java’s wrapper classes, such as Integer and Double? Answer: The valueOf() method converts a primitive data type to its corresponding wrapper class object. For example, Integer.valueOf(42) creates an Integer object with the value 42.

22. How can you check if a string is empty or contains only whitespace characters in Java? Answer: You can use the isEmpty() method to check if a string is empty. To check if it contains only whitespace characters, you can use a regular expression or the trim() method and then check if the resulting string is empty.

23. Explain the purpose of the intern() method in Java’s String class. Answer: The intern() method returns a canonical representation of a string. It checks the string pool for an equal string and returns the reference if found. This can be useful for optimizing memory usage and improving performance when working with a large number of strings.

24. What is the difference between StringBuffer and StringBuilder in terms of thread safety? Answer: StringBuffer is thread-safe, as its methods are synchronized, making it suitable for multi-threaded environments. StringBuilder is not thread-safe, which makes it more efficient for single-threaded scenarios.

25. How do you compare the contents of two strings without considering their case? Answer: To compare two strings without considering case, you can convert both strings to lowercase or uppercase using the toLowerCase() or toUpperCase() method and then use the equals() method for comparison.

Conclusion In the realm of Java programming, the ability to manipulate strings effectively is a key skill that every developer must possess. This article has provided you with an in-depth exploration of Java String interview questions and answers. Remember that success in interviews isn’t solely about memorizing responses; it’s about grasping the underlying concepts and demonstrating problem-solving skills.

As you prepare for your Java interview, practice is your best ally. Experiment with different string manipulation techniques, solve real-world coding challenges, and seek feedback from experienced developers or mentors. Building confidence comes with hands-on experience and a deep understanding of Java’s String class.

Ultimately, your performance in the interview will hinge on your ability to apply your knowledge to practical scenarios and communicate effectively with your prospective employer. By mastering these interview questions and the principles they represent, you’ll be well on your way to acing your Java interview and advancing your career as a Java developer.

FAQ (Frequently Asked Questions) Related to Java String Interview Questions:

Here are some FAQs related to Java String Interview Questions.

1. Why is string manipulation important in Java interviews? Answer: String manipulation is a fundamental skill in Java development, as strings are commonly used to store and process data. Interviewers often assess candidates’ string-handling abilities to gauge their overall Java programming skills.

2. How should I prepare effectively for a Java String interview? Answer: To prepare effectively, study core string manipulation concepts, practice writing code to manipulate strings, and understand the various methods available in Java’s String class. Review the questions and answers in this article and work on coding challenges related to string manipulation.

3. What are some key methods in Java’s String class that I should be familiar with? Answer: Important methods in Java’s String class include charAt(), length(), substring(), concat(), equals(), equalsIgnoreCase(), startsWith(), endsWith(), contains(), indexOf(), lastIndexOf(), split(), trim(), and many more. Familiarize yourself with their usage and applications.

4. Is it necessary to memorize all the answers to these interview questions? Answer: While memorization can be helpful, it’s more important to understand the concepts and be able to apply them in different scenarios. Interviewers often appreciate candidates who can adapt their knowledge to real-world problems.

5. How can I stand out during a Java String interview? Answer: To stand out, demonstrate not only your knowledge of string manipulation but also your problem-solving skills. Be prepared to explain your thought process and how you arrive at solutions. Sharing examples of projects where you’ve effectively used string manipulation can also make a strong impression.

6. What are some common challenges in string manipulation that Java developers face? Answer: Common challenges include handling special characters, working with character encoding, efficiently concatenating or splitting strings, and performing complex text transformations. Being aware of these challenges and knowing how to overcome them is valuable during interviews and real-world Java development.

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Java String Interview Questions

string interview questions problem solving

Introduction

Java is the most popular programming language among developers. Even after new programming languages are developing, JAVA seems to get more widespread year on year. One of the reasons behind this is its platform independence. Programs can run on different computers as long as the Java runtime environment is installed.

top string programming interview question in Java

This is the reason why JAVA is a favorite among interviewers. Sometimes, interviewers focus mainly on String Data Structure . But string interview questions are in itself so vast that you won't be able to focus on other concepts.

With the little time you had while preparing for your interviews, you can go through the string interview questions covered in this blog which can help you in your upcoming interviews.

The blog covers Intermediate and Advanced level string programming questions in java with answers so that you can have a clearer understanding.

What is String in Java?

A string in Java is a group of characters that is an instance of an object belonging to the java.lang class. The string class in Java is used to produce and edit strings. A string cannot have its value modified after it has been generated. In Java , strings are quite unique. Programmers can employ strings in accordance with the needs of their projects because they support a wide range of additional functionalities.

Also read:-  Fibonacci Series in Java

string interview questions problem solving

Java String Interview Questions for Freshers

1. what are the different ways to create string objects.

  String objects can be created in two ways:

  • Using the 'new' operator.
  • Using double-quotes.   

Several constructors are also available in the String class to create strings from a char array, byte array, StringBuilder, and StringBuffer.

When the String is created with the double quotes, JVM searches it for in the string pool; if the same value is found, it returns the reference to that String else creates a new object with the new value provided.

In the other case, if the String is created with the 'new' operator, then JVM creates a new object but not in the string pool. If we want to create the object in the string pool, we can use the intern() method.

2. Difference between String, StringBuffer, and StringBuilder in java

There are three classes to represent a sequence of characters: String, StringBuffer, and StringBuilder. 

3. Why is string made immutable in JAVA?

Immutable means unmodifiable or unchangeable.

Security is the major reason why strings in Java are made to be immutable. Strings in Java can be used to access data sources like files, databases, or even objects found across networks. Even sometimes, strings store passwords and usernames, which can't be modified once created.

4. How to compare two strings in java?

We can compare two strings using the equals() method. Another method is to use the '==' operator but try to avoid this method to compare two strings.

The reason behind this 'equals()' method compares the values of the two strings, whereas the '==' operator compares the reference in the memory.

Must Read:  Java System Out Println

5. How can you remove all the white spaces in a string?

Removal of white spaces in the String is termed as 'Squeezing.' Trimming from the left, right, and trimming the white spaces together combined in 'Squeezing.'

The output of the program is:

6. Explain String pool in Java?

The Java Virtual Machine (JVM) stores string literals in the string pool to reduce memory use. In order to ensure that strings with the same content correspond to the same memory address and to minimise memory overhead, identical string literals are stored only once. This increases efficiency.

7. How many objects are created in the following code snippet?

Two objects are created in the above code snippet. 

  • s1 String is created in the string constant pool as it is created by string literals.
  • s2 String is created in heap memory as it is created by the 'new' operator. No new object will be created in the string constant pool as it is already created by s1.  

8.   How many objects are created in the following code snippet?

Three objects will be created.

  • For string s1, two objects will be created, one in heap memory and the other in String constant pool.
  • For string s2, only one object will be created in heap memory, but no new object will be created in the string constant pool as the object with the same value is already present in the string constant pool.  

9. Difference between string in C and string in java.

  • C string is a null-terminated character array whereas String in Java is an object.
  • String objects in java allow us to call various methods like substring(), toLowerCase(), length().  

10. What does the string intern() method do?

When the intern method is invoked, if the String constant pool already contains a string equal to the String object as determined by the equals(Object) method, the String from the pool is returned.

Otherwise, the String object is added to the pool, and a reference to the String object is returned.

The task of the intern() method is to put String (which is passed to the intern method) into the string constant pool.

11. How can you split the string in java?

split() method of java.lang.String is used to split a comma-separated String. We can also use StringTokenizer to split the comma-separated String, but the split() method is easier and better to use as it returns an array of strings that we can further manipulate in the code.

12. Write a program to remove a given character from a string.

We can use the replaceAll() method to replace all the string occurrences in the given String. But here, a character is given as an argument. So, first, we have to convert this character into a string; then, by using the replaceAll() method, we can remove all the occurrences of the given character in the required String.

13. Why string is not used for storing the passwords rather a char array is preferred for the same?

String is immutable in Java and stored in the string constant pool. Once the string object is created, it is stored in the pool unless garbage is collected.

In the case of passwords, if String is used, it will be available in the memory for a longer duration. It will be a security risk as anyone with access to the memory dump can access the password.

On the other hand, if we use a char array for storing the passwords, we can set it to blank once we are done creating it. So we can control for how long the password will be available in the memory. That's why a char array is preferred for storing the passwords rather than String.

14. Which object is popular as the HashMap key and why?

String is the popular HashMap key.  This is because String is immutable in Java. So, the hashcode of the String is cached every time it is created and doesn't need to be calculated again. This makes the processing faster than other HashMap keys. 

15. How will you create an immutable class in java?

You can create an immutable class in Java by implementing the following points:

  • First, make the class as final such that the class cannot be further inherited.
  • Then, make all the data members private such that they will not be accessible from outside the class.
  • Do not provide setter methods for the variables.
  • Deep copy of objects should be performed in the getter methods.

Java String Interview Questions for Experienced

16. explain character encoding. what is the difference between utf-8 and utf-16.

  • Encoding is the way to convert the data from one form to another.
  • Character encoding refers to the method when a character is represented in bytes.
  • UTF-8 uses 1 byte or 8 bits of memory to store the character, whereas UTF-16 uses 2 bytes or 16 bits of memory to store the character.

17. How does the substring() method fix memory leakage?

Substring shares the same character array as the String. If the original String is too large, it will lead to a memory leak, and sometimes it will not be retained.

Then, the original String will be retained by the substring as the size of the substring is smaller than the original String. It will further result in the prevention of large arrays being garbage collected. 

18. Write a program to check whether the two given strings are anagrams.

Two strings are said to be anagrams if the two strings contain the same set of characters, but the order can be different.

For example: "coding" and "dincog" are anagrams. "ninjas" and "jasnni" are anagrams.

There are two approaches to solve this problem:

Approach 1: This approach involves sorting both the strings lexicographically and then comparing both strings. This approach will cost O(N * log(N) + M * log(M)) time where 'M' and 'N' represent the length of two strings. 

Approach 2: This approach involves storing the frequencies of each character of the two strings and then comparing the occurrence of the characters in the two strings. This approach will cost O(N + M) time and O(26) space where 'N' and 'M' represent the length of the two strings.

For the code and algorithm, you can refer to the link -  Anagrams .

Also read, Permutation of string

19. Write a program to print all permutations of String in Java.

Let's say a given string is "abc" so all possible permutations of this string will be "abc", "acb", "bac", "bca", "cab", "cba". So in this question, we have to generate all the permutations of the characters in the given String.

Approach 1: This approach follows backtracking. In this, a character is made to be fixed at a position, and permutations of the rest of the characters will be computed. This approach will cost O(N! * log(N!)) time and O(N * N!) space.

Approach 2: This approach is way more optimized than Approach 1. In this approach, the first permutation will be the String sorted in increasing order, and the last permutation will be the String sorted in decreasing order. This approach will cost O(N * N!) time and O(N * N!) space.

20. Write a program to swap two string variables without using a third variable in Java.

Suppose we have two strings, String a = "Coding" and String b = "Ninjas." After swapping, the result should be a = "Ninjas" and b = "Coding."

For this we first concatenate string b to string a, So a = “CodingNinjas”. Now we will store the substring starting from index 0 and of length = a.length() - b.length() in string b. Now b = “Coding”.

Now store the substring from index = b.length() till the end of the String a in String a. After this, String a = "Ninjas."

You can refer to the below code snippet for the logic.

The output for the code is:

21. What is StringTokenizer in Java?

To break the String into tokens, Java.util.StringTokenizer is used. StringTokenizer doesn't provide the facility to differentiate identifiers, quoted strings, and numbers like the StreamTokenizer class.

There are six useful methods of the StreamTokenizer class:

  • String nextToken() - This will return the next token from the StringTokenizer cobject.
  • Object nextElement() - This method is same as nextToken() but it will return an object.
  • boolean hasMoreTokens() - This method checks if there are more tokens available or not.
  • int countTokens() - This method returns the total number of tokens 
  • String nextToken(String delim) - This method returns the next token based on the delimiter.
  • Boolean hasMoreElements() - This method is same as hasMoreTokens().  

You can also check about  Java Tokens here.

Most Asked Java String Programming Questions

22. write a program in java to reverse the order of words in a string without using the reverse() method..

In this question, you will be given a string of space-separated words like "hey there hope you are having a good time." You have to reverse the order of words in the given String like "time good a having are you hope there hey."

The approach is to use an array to store the words of the String. Now traverse the array in the reverse direction and append the words again in the given String.

This approach will cost O(N) time and O(N) space, where 'N' denotes the length of the given String.

You can refer to the link for the code and algorithm -  Reverse the order of words in a string .

23. Suppose there is a code in which a lot of string modification and string concatenation is going on. Which class among StringBuffer, String, and StringBuilder, will improve the performance of the code, keeping thread-safety of the code in mind?

If we use the String class, because of its immutable nature, it will create a new object after every modification in the String, which will badly affect the performance of the code.

The StringBuilder class is not thread-safe because StringBuilder is not synchronized.

So, in this scenario, StringBuffer will give better performance.

24.Why is Java provided with String constant pool as we can store the objects in heap memory?

String constant pool provides the facility of reusability of the existing string objects. When a new string object is created using the string literals, then JVM first checks in the pool if this String already exists or not. If it exists, then it will reference the existing String rather than creating a new object. This will help in the speeding up of the application and also helps in saving the memory as no two objects will have the same content.

25. How can a Java string be converted into a byte array?

The getBytes() function of the string in Java allows you to choose the character encoding and converts a string into a byte array. Here's an example:

In this instance, the string is transformed into a byte array using the UTF-8 character encoding using the getBytes() method. Depending on your needs, you can substitute "UTF-8" with other recognised character encodings like "UTF-16". Remember that selecting a particular encoding is crucial to ensuring precise character-to-byte translation.

26.Write a code in Java to prove that String objects are immutable.

Generate two string objects using string literals, say s1 = "codingninjas" and s2 = "codingninjas." As string objects generated with string literals are stored in the string constant pool, any two objects can't have the same values. Therefore, both s1 and s2 will be pointing to the same object.

Then s1==s2 will return true.

Let’s just modify s1 by concatenating “article” as s1 = s1 + “article”. After this s2 = "codingninjasarticle". This statement will concatenate "article" to the object which s1 is pointing to and reassigns reference of that object back to s1.

Now, s1==s2 will give false output as s1 and s2 are now pointing to different objects in the pool as when we modified s1, a new object is created in the pool, and its reference is assigned to s1.

For clarification, refer to the below code snippet.  

27. What will be the output of the following code?

The output of the above code will be 411. The reason is the print statement has character literals in single quotes, so instead of concatenation, the corresponding ASCII value of each character is added, and the result is displayed as 411.

28. What is the difference between s1.equals("book") and "book" .equals(s1) where s1 represents the object of a string?

If the s1 value is "book", then both statements will return true. The difference arises when s1 will be a null value. In that case, s1.equals("book") will throw the null pointer exception, and on the other hand "book" .equals(s1) will return false.

29. What will be the output of the following code?

The output of this code will be CODING because s2 will be assigned to s1. The confusion arises between '==' and '=' operators. That's why this question is a simple yet tricky one. You can learn more about Java code compiler here.

30.   What will be the output of the following code?

The output of this code will be false as s2 is not of a type string.

Frequently Asked Questions

What are the 3 different types of strings.

The first type uses double quotes to construct string literals. The second type, produced by the new keyword, is string objects. Last but not least, Java 1.5 introduced the StringBuilder class for effective management of mutable character sequences known as string buffers.

What is the main purpose of strings in Java?

Strings in Java are mostly used to represent a group of characters. Java programming makes considerable use of string for text processing and data manipulation. They are an effective tool for Java developer because they are immutable, simple, and provide a wide range of methods for working with string.

How to solve a string problem in Java? 

To solve a string problem in Java, you can utilize a variety of built-in methods like charAt(), substring(), or regular expressions. Alternatively, custom algorithms can be created for specific tasks like palindrome checks, pattern matching, or string manipulation.

Why strings are immutable in Java?

Strings are immutable in Java for several reasons. Immutability enhances security by preventing unauthorized modification of sensitive data. It also improves performance by enabling caching and optimization. Furthermore, it ensures thread safety, making strings safe to share across multiple threads in a concurrent environment. This immutability simplifies memory management and guarantees that once a string is created, its value remains unchanged.

This article discussed the String programming Interview Questions of Java from the intermediate to advanced level. You can practice the same String programming Interview Questions for Python as well. Once you are done with this, you can check out our  Interview Preparation Course to level up your programming journey and get placed at your dream company.

Related Links:

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You can also consider our paid  courses such as   DSA in Java   to give your career an edge over others!

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15 Common Problem-Solving Interview Questions

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In an interview for a big tech company, I was asked if I’d ever resolved a fight — and the exact way I went about handling it. I felt blindsided, and I stammered my way through an excuse of an answer.

It’s a familiar scenario to fellow technical job seekers — and one that risks leaving a sour taste in our mouths. As candidate experience becomes an increasingly critical component of the hiring process, recruiters need to ensure the problem-solving interview questions they prepare don’t dissuade talent in the first place. 

Interview questions designed to gauge a candidate’s problem-solving skills are more often than not challenging and vague. Assessing a multifaceted skill like problem solving is tricky — a good problem solver owns the full solution and result, researches well, solves creatively and takes action proactively. 

It’s hard to establish an effective way to measure such a skill. But it’s not impossible.

We recommend taking an informed and prepared approach to testing candidates’ problem-solving skills . With that in mind, here’s a list of a few common problem-solving interview questions, the science behind them — and how you can go about administering your own problem-solving questions with the unique challenges of your organization in mind.

Key Takeaways for Effective Problem-Solving Interview Questions

  • Problem solving lies at the heart of programming. 
  • Testing a candidate’s problem-solving skills goes beyond the IDE. Problem-solving interview questions should test both technical skills and soft skills.
  • STAR, SOAR and PREP are methods a candidate can use to answer some non-technical problem-solving interview questions.
  • Generic problem-solving interview questions go a long way in gauging a candidate’s fit. But you can go one step further by customizing them according to your company’s service, product, vision, and culture. 

Technical Problem-Solving Interview Question Examples

Evaluating a candidates’ problem-solving skills while using coding challenges might seem intimidating. The secret is that coding challenges test many things at the same time — like the candidate’s knowledge of data structures and algorithms, clean code practices, and proficiency in specific programming languages, to name a few examples.

Problem solving itself might at first seem like it’s taking a back seat. But technical problem solving lies at the heart of programming, and most coding questions are designed to test a candidate’s problem-solving abilities.

Here are a few examples of technical problem-solving questions:

1. Mini-Max Sum  

This well-known challenge, which asks the interviewee to find the maximum and minimum sum among an array of given numbers, is based on a basic but important programming concept called sorting, as well as integer overflow. It tests the candidate’s observational skills, and the answer should elicit a logical, ad-hoc solution.

2. Organizing Containers of Balls  

This problem tests the candidate’s knowledge of a variety of programming concepts, like 2D arrays, sorting and iteration. Organizing colored balls in containers based on various conditions is a common question asked in competitive examinations and job interviews, because it’s an effective way to test multiple facets of a candidate’s problem-solving skills.

3. Build a Palindrome

This is a tough problem to crack, and the candidate’s knowledge of concepts like strings and dynamic programming plays a significant role in solving this challenge. This problem-solving example tests the candidate’s ability to think on their feet as well as their ability to write clean, optimized code.

4. Subarray Division

Based on a technique used for searching pairs in a sorted array ( called the “two pointers” technique ), this problem can be solved in just a few lines and judges the candidate’s ability to optimize (as well as basic mathematical skills).

5. The Grid Search 

This is a problem of moderate difficulty and tests the candidate’s knowledge of strings and searching algorithms, the latter of which is regularly tested in developer interviews across all levels.

Common Non-Technical Problem-Solving Interview Questions 

Testing a candidate’s problem-solving skills goes beyond the IDE . Everyday situations can help illustrate competency, so here are a few questions that focus on past experiences and hypothetical situations to help interviewers gauge problem-solving skills.

1. Given the problem of selecting a new tool to invest in, where and how would you begin this task? 

Key Insight : This question offers insight into the candidate’s research skills. Ideally, they would begin by identifying the problem, interviewing stakeholders, gathering insights from the team, and researching what tools exist to best solve for the team’s challenges and goals. 

2. Have you ever recognized a potential problem and addressed it before it occurred? 

Key Insight: Prevention is often better than cure. The ability to recognize a problem before it occurs takes intuition and an understanding of business needs. 

3. A teammate on a time-sensitive project confesses that he’s made a mistake, and it’s putting your team at risk of missing key deadlines. How would you respond?

Key Insight: Sometimes, all the preparation in the world still won’t stop a mishap. Thinking on your feet and managing stress are skills that this question attempts to unearth. Like any other skill, they can be cultivated through practice.

4. Tell me about a time you used a unique problem-solving approach. 

Key Insight: Creativity can manifest in many ways, including original or novel ways to tackle a problem. Methods like the 10X approach and reverse brainstorming are a couple of unique approaches to problem solving. 

5. Have you ever broken rules for the “greater good?” If yes, can you walk me through the situation?

Key Insight: “Ask for forgiveness, not for permission.” It’s unconventional, but in some situations, it may be the mindset needed to drive a solution to a problem.

6. Tell me about a weakness you overcame at work, and the approach you took. 

Key Insight: According to Compass Partnership , “self-awareness allows us to understand how and why we respond in certain situations, giving us the opportunity to take charge of these responses.” It’s easy to get overwhelmed when faced with a problem. Candidates showing high levels of self-awareness are positioned to handle it well.

7. Have you ever owned up to a mistake at work? Can you tell me about it?

Key Insight: Everybody makes mistakes. But owning up to them can be tough, especially at a workplace. Not only does it take courage, but it also requires honesty and a willingness to improve, all signs of 1) a reliable employee and 2) an effective problem solver.

8. How would you approach working with an upset customer?

Key Insight: With the rise of empathy-driven development and more companies choosing to bridge the gap between users and engineers, today’s tech teams speak directly with customers more frequently than ever before. This question brings to light the candidate’s interpersonal skills in a client-facing environment.

9. Have you ever had to solve a problem on your own, but needed to ask for additional help? How did you go about it? 

Key Insight: Knowing when you need assistance to complete a task or address a situation is an important quality to have while problem solving. This questions helps the interviewer get a sense of the candidate’s ability to navigate those waters. 

10. Let’s say you disagree with your colleague on how to move forward with a project. How would you go about resolving the disagreement?

Key Insight: Conflict resolution is an extremely handy skill for any employee to have; an ideal answer to this question might contain a brief explanation of the conflict or situation, the role played by the candidate and the steps taken by them to arrive at a positive resolution or outcome. 

Strategies for Answering Problem-Solving Questions

If you’re a job seeker, chances are you’ll encounter this style of question in your various interview experiences. While problem-solving interview questions may appear simple, they can be easy to fumble — leaving the interviewer without a clear solution or outcome. 

It’s important to approach such questions in a structured manner. Here are a few tried-and-true methods to employ in your next problem-solving interview.

1. Shine in Interviews With the STAR Method

S ituation, T ask, A ction, and R esult is a great method that can be employed to answer a problem-solving or behavioral interview question. Here’s a breakdown of these steps:

  • Situation : A good way to address almost any interview question is to lay out and define the situation and circumstances. 
  • Task : Define the problem or goal that needs to be addressed. Coding questions are often multifaceted, so this step is particularly important when answering technical problem-solving questions.
  • Action : How did you go about solving the problem? Try to be as specific as possible, and state your plan in steps if you can.
  • Result : Wrap it up by stating the outcome achieved. 

2. Rise above difficult questions using the SOAR method

A very similar approach to the STAR method, SOAR stands for S ituation, O bstacle, A ction, and R esults .

  • Situation: Explain the state of affairs. It’s important to steer clear of stating any personal opinions in this step; focus on the facts.
  • Obstacle: State the challenge or problem you faced.
  • Action: Detail carefully how you went about overcoming this obstacle.
  • Result: What was the end result? Apart from overcoming the obstacle, did you achieve anything else? What did you learn in the process? 

3. Do It the PREP Way

Traditionally used as a method to make effective presentations, the P oint, R eason, E xample, P oint method can also be used to answer problem-solving interview questions.  

  • Point : State the solution in plain terms. 
  • Reasons: Follow up the solution by detailing your case — and include any data or insights that support your solution. 
  • Example: In addition to objective data and insights, drive your answer home by contextualizing the solution in a real-world example.
  • Point : Reiterate the solution to make it come full circle.

How to Customize Problem-Solving Interview Questions 

Generic problem-solving interview questions go a long way in gauging a candidate’s skill level, but recruiters can go one step further by customizing these problem-solving questions according to their company’s service, product, vision, or culture. 

Here are some tips to do so:

  • Break down the job’s responsibilities into smaller tasks. Job descriptions may contain ambiguous responsibilities like “manage team projects effectively.” To formulate an effective problem-solving question, envision what this task might look like in a real-world context and develop a question around it.  
  • Tailor questions to the role at hand. Apart from making for an effective problem-solving question, it gives the candidate the impression you’re an informed technical recruiter. For example, an engineer will likely have attended many scrums. So, a good question to ask is: “Suppose you notice your scrums are turning unproductive. How would you go about addressing this?” 
  • Consider the tools and technologies the candidate will use on the job. For example, if Jira is the primary project management tool, a good problem-solving interview question might be: “Can you tell me about a time you simplified a complex workflow — and the tools you used to do so?”
  • If you don’t know where to start, your company’s core values can often provide direction. If one of the core values is “ownership,” for example, consider asking a question like: “Can you walk us through a project you owned from start to finish?” 
  • Sometimes, developing custom content can be difficult even with all these tips considered. Our platform has a vast selection of problem-solving examples that are designed to help recruiters ask the right questions to help nail their next technical interview.

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Top 72 Swift Interview Questions

25+ JavaScript Coding Interview Questions (SOLVED with CODE)

Having a JavaScript Coding Interview Session on this week? Fear not, we got your covered! Check that ultimate list of 25 advanced and tricky JavaScript Coding Interview Questions and Challenges to crack on your next senior web developer interview and got your next six-figure job offer in no time!

Q1 :   Explain what a callback function is and provide a simple example

A callback function is a function that is passed to another function as an argument and is executed after some operation has been completed. Below is an example of a simple callback function that logs to the console after some operations have been completed.

Q2 :   Given a string, reverse each word in the sentence

For example Welcome to this Javascript Guide! should be become emocleW ot siht tpircsavaJ !ediuG

Q3 :   How to check if an object is an array or not? Provide some code.

The best way to find whether an object is instance of a particular class or not using toString method from Object.prototype

One of the best use cases of type checking of an object is when we do method overloading in JavaScript. For understanding this let say we have a method called greet which take one single string and also a list of string, so making our greet method workable in both situation we need to know what kind of parameter is being passed, is it single value or list of value?

However, in above implementation it might not necessary to check type for array, we can check for single value string and put array logic code in else block, let see below code for the same.

Now it's fine we can go with above two implementations, but when we have a situation like a parameter can be single value , array , and object type then we will be in trouble.

Coming back to checking type of object, As we mentioned that we can use Object.prototype.toString

If you are using jQuery then you can also used jQuery isArray method:

FYI jQuery uses Object.prototype.toString.call internally to check whether an object is an array or not.

In modern browser, you can also use:

Array.isArray is supported by Chrome 5, Firefox 4.0, IE 9, Opera 10.5 and Safari 5

Q4 :   How to empty an array in JavaScript?

How could we empty the array above?

Above code will set the variable arrayList to a new empty array. This is recommended if you don't have references to the original array arrayList anywhere else because It will actually create a new empty array. You should be careful with this way of empty the array, because if you have referenced this array from another variable, then the original reference array will remain unchanged, Only use this way if you have only referenced the array by its original variable arrayList .

For Instance:

Above code will clear the existing array by setting its length to 0. This way of empty the array also update all the reference variable which pointing to the original array. This way of empty the array is useful when you want to update all the another reference variable which pointing to arrayList .

Above implementation will also work perfectly. This way of empty the array will also update all the references of the original array.

Above implementation can also empty the array. But not recommended to use often.

Q5 :   How would you check if a number is an integer?

A very simply way to check if a number is a decimal or integer is to see if there is a remainder left when you divide by 1.

Q6 :   Implement enqueue and dequeue using only two stacks

Enqueue means to add an element, dequeue to remove an element.

Q7 :   Make this work

Q8 :   write a "mul" function which will properly when invoked as below syntax.

Here mul function accept the first argument and return anonymous function which take the second parameter and return anonymous function which take the third parameter and return multiplication of arguments which is being passed in successive

In JavaScript function defined inside has access to outer function variable and function is the first class object so it can be returned by function as well and passed as argument in another function.

  • A function is an instance of the Object type
  • A function can have properties and has a link back to its constructor method
  • Function can be stored as variable
  • Function can be pass as a parameter to another function
  • Function can be returned from function

Q9 :   Write a function that would allow you to do this?

You can create a closure to keep the value passed to the function createBase even after the inner function is returned. The inner function that is being returned is created within an outer function, making it a closure, and it has access to the variables within the outer function, in this case the variable baseNumber .

Q10 :   FizzBuzz Challenge

Create a for loop that iterates up to 100 while outputting "fizz" at multiples of 3 , "buzz" at multiples of 5 and "fizzbuzz" at multiples of 3 and 5 .

Check out this version of FizzBuzz:

Q11 :   Given two strings, return true if they are anagrams of one another

For example: Mary is an anagram of Army

Q12 :   How would you use a closure to create a private counter?

You can create a function within an outer function (a closure) that allows you to update a private variable but the variable wouldn't be accessible from outside the function without the use of a helper function.

Q13 :   Provide some examples of non-bulean value coercion to a boolean one

The question is when a non-boolean value is coerced to a boolean, does it become true or false , respectively?

The specific list of "falsy" values in JavaScript is as follows:

  • "" (empty string)
  • 0 , -0 , NaN (invalid number)
  • null , undefined

Any value that's not on this "falsy" list is "truthy." Here are some examples of those:

  • [ ] , [ 1, "2", 3 ] (arrays)
  • { } , { a: 42 } (objects)
  • function foo() { .. } (functions)

Q14 :   What will be the output of the following code?

Above code would give output 1undefined . If condition statement evaluate using eval so eval(function f() {}) which return function f() {} which is true so inside if statement code execute. typeof f return undefined because if statement code execute at run time, so statement inside if condition evaluated at run time.

Above code will also output 1undefined .

Q15 :   What will the following code output?

The code above will output 5 even though it seems as if the variable was declared within a function and can't be accessed outside of it. This is because

is interpreted the following way:

But b is not declared anywhere in the function with var so it is set equal to 5 in the global scope .

Q16 :   Write a function that would allow you to do this

You can create a closure to keep the value of a even after the inner function is returned. The inner function that is being returned is created within an outer function, making it a closure, and it has access to the variables within the outer function, in this case the variable a .

Q17 :   How does the this keyword work? Provide some code examples

In JavaScript this always refers to the “owner” of the function we're executing, or rather, to the object that a function is a method of.

Q18 :   How would you create a private variable in JavaScript?

To create a private variable in JavaScript that cannot be changed you need to create it as a local variable within a function. Even if the function is executed the variable cannot be accessed outside of the function. For example:

To access the variable, a helper function would need to be created that returns the private variable.

Q19 :   What is Closure in JavaScript? Provide an example

A closure is a function defined inside another function (called parent function) and has access to the variable which is declared and defined in parent function scope.

The closure has access to variable in three scopes:

  • Variable declared in his own scope
  • Variable declared in parent function scope
  • Variable declared in global namespace

innerFunction is closure which is defined inside outerFunction and has access to all variable which is declared and defined in outerFunction scope. In addition to this function defined inside function as closure has access to variable which is declared in global namespace .

Output of above code would be:

Q20 :   What will be the output of the following code?

Above code will output 0 as output. delete operator is used to delete a property from an object. Here x is not an object it's local variable . delete operator doesn't affect local variable.

Q21 :   What will be the output of the following code?

Above code will output xyz as output. Here emp1 object got company as prototype property. delete operator doesn't delete prototype property.

emp1 object doesn't have company as its own property. You can test it like:

However, we can delete company property directly from Employee object using delete Employee.company or we can also delete from emp1 object using __proto__ property delete emp1.__proto__.company .

Q22 :   What will the following code output?

This will surprisingly output false because of floating point errors in internally representing certain numbers. 0.1 + 0.2 does not nicely come out to 0.3 but instead the result is actually 0.30000000000000004 because the computer cannot internally represent the correct number. One solution to get around this problem is to round the results when doing arithmetic with decimal numbers.

Q23 :   When would you use the bind function?

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.

A good use of the bind function is when you have a particular function that you want to call with a specific this value. You can then use bind to pass a specific object to a function that uses a this reference.

Q24 :   Write a recursive function that performs a binary search

Q25 :   describe the revealing module pattern design pattern.

A variation of the module pattern is called the Revealing Module Pattern . The purpose is to maintain encapsulation and reveal certain variables and methods returned in an object literal. The direct implementation looks like this:

An obvious disadvantage of it is unable to reference the private methods

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Clean Architecture provides a clear and modular structure for building software systems, separating business rules from implementation details. It promotes maintainability by allowing for easier updates and changes to specific components without affe...

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string interview questions problem solving

Top 20 Problem Solving Interview Questions (Example Answers Included)

Mike Simpson 0 Comments

string interview questions problem solving

By Mike Simpson

When candidates prepare for interviews, they usually focus on highlighting their leadership, communication, teamwork, and similar crucial soft skills . However, not everyone gets ready for problem-solving interview questions. And that can be a big mistake.

Problem-solving is relevant to nearly any job on the planet. Yes, it’s more prevalent in certain industries, but it’s helpful almost everywhere.

Regardless of the role you want to land, you may be asked to provide problem-solving examples or describe how you would deal with specific situations. That’s why being ready to showcase your problem-solving skills is so vital.

If you aren’t sure who to tackle problem-solving questions, don’t worry, we have your back. Come with us as we explore this exciting part of the interview process, as well as some problem-solving interview questions and example answers.

What Is Problem-Solving?

When you’re trying to land a position, there’s a good chance you’ll face some problem-solving interview questions. But what exactly is problem-solving? And why is it so important to hiring managers?

Well, the good folks at Merriam-Webster define problem-solving as “the process or act of finding a solution to a problem.” While that may seem like common sense, there’s a critical part to that definition that should catch your eye.

What part is that? The word “process.”

In the end, problem-solving is an activity. It’s your ability to take appropriate steps to find answers, determine how to proceed, or otherwise overcome the challenge.

Being great at it usually means having a range of helpful problem-solving skills and traits. Research, diligence, patience, attention-to-detail , collaboration… they can all play a role. So can analytical thinking , creativity, and open-mindedness.

But why do hiring managers worry about your problem-solving skills? Well, mainly, because every job comes with its fair share of problems.

While problem-solving is relevant to scientific, technical, legal, medical, and a whole slew of other careers. It helps you overcome challenges and deal with the unexpected. It plays a role in troubleshooting and innovation. That’s why it matters to hiring managers.

How to Answer Problem-Solving Interview Questions

Okay, before we get to our examples, let’s take a quick second to talk about strategy. Knowing how to answer problem-solving interview questions is crucial. Why? Because the hiring manager might ask you something that you don’t anticipate.

Problem-solving interview questions are all about seeing how you think. As a result, they can be a bit… unconventional.

These aren’t your run-of-the-mill job interview questions . Instead, they are tricky behavioral interview questions . After all, the goal is to find out how you approach problem-solving, so most are going to feature scenarios, brainteasers, or something similar.

So, having a great strategy means knowing how to deal with behavioral questions. Luckily, there are a couple of tools that can help.

First, when it comes to the classic approach to behavioral interview questions, look no further than the STAR Method . With the STAR method, you learn how to turn your answers into captivating stories. This makes your responses tons more engaging, ensuring you keep the hiring manager’s attention from beginning to end.

Now, should you stop with the STAR Method? Of course not. If you want to take your answers to the next level, spend some time with the Tailoring Method , too.

With the Tailoring Method, it’s all about relevance. So, if you get a chance to choose an example that demonstrates your problem-solving skills, this is really the way to go.

We also wanted to let you know that we created an amazing free cheat sheet that will give you word-for-word answers for some of the toughest interview questions you are going to face in your upcoming interview. After all, hiring managers will often ask you more generalized interview questions!

Click below to get your free PDF now:

Get Our Job Interview Questions & Answers Cheat Sheet!

FREE BONUS PDF CHEAT SHEET: Get our " Job Interview Questions & Answers PDF Cheat Sheet " that gives you " word-word sample answers to the most common job interview questions you'll face at your next interview .

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Top 3 Problem-Solving-Based Interview Questions

Alright, here is what you’ve been waiting for: the problem-solving questions and sample answers.

While many questions in this category are job-specific, these tend to apply to nearly any job. That means there’s a good chance you’ll come across them at some point in your career, making them a great starting point when you’re practicing for an interview.

So, let’s dive in, shall we? Here’s a look at the top three problem-solving interview questions and example responses.

1. Can you tell me about a time when you had to solve a challenging problem?

In the land of problem-solving questions, this one might be your best-case scenario. It lets you choose your own problem-solving examples to highlight, putting you in complete control.

When you choose an example, go with one that is relevant to what you’ll face in the role. The closer the match, the better the answer is in the eyes of the hiring manager.

EXAMPLE ANSWER:

“While working as a mobile telecom support specialist for a large organization, we had to transition our MDM service from one vendor to another within 45 days. This personally physically handling 500 devices within the agency. Devices had to be gathered from the headquarters and satellite offices, which were located all across the state, something that was challenging even without the tight deadline. I approached the situation by identifying the location assignment of all personnel within the organization, enabling me to estimate transit times for receiving the devices. Next, I timed out how many devices I could personally update in a day. Together, this allowed me to create a general timeline. After that, I coordinated with each location, both expressing the urgency of adhering to deadlines and scheduling bulk shipping options. While there were occasional bouts of resistance, I worked with location leaders to calm concerns and facilitate action. While performing all of the updates was daunting, my approach to organizing the event made it a success. Ultimately, the entire transition was finished five days before the deadline, exceeding the expectations of many.”

2. Describe a time where you made a mistake. What did you do to fix it?

While this might not look like it’s based on problem-solving on the surface, it actually is. When you make a mistake, it creates a challenge, one you have to work your way through. At a minimum, it’s an opportunity to highlight problem-solving skills, even if you don’t address the topic directly.

When you choose an example, you want to go with a situation where the end was positive. However, the issue still has to be significant, causing something negative to happen in the moment that you, ideally, overcame.

“When I first began in a supervisory role, I had trouble setting down my individual contributor hat. I tried to keep up with my past duties while also taking on the responsibilities of my new role. As a result, I began rushing and introduced an error into the code of the software my team was updating. The error led to a memory leak. We became aware of the issue when the performance was hindered, though we didn’t immediately know the cause. I dove back into the code, reviewing recent changes, and, ultimately, determined the issue was a mistake on my end. When I made that discovery, I took several steps. First, I let my team know that the error was mine and let them know its nature. Second, I worked with my team to correct the issue, resolving the memory leak. Finally, I took this as a lesson about delegation. I began assigning work to my team more effectively, a move that allowed me to excel as a manager and help them thrive as contributors. It was a crucial learning moment, one that I have valued every day since.”

3. If you identify a potential risk in a project, what steps do you take to prevent it?

Yes, this is also a problem-solving question. The difference is, with this one, it’s not about fixing an issue; it’s about stopping it from happening. Still, you use problem-solving skills along the way, so it falls in this question category.

If you can, use an example of a moment when you mitigated risk in the past. If you haven’t had that opportunity, approach it theoretically, discussing the steps you would take to prevent an issue from developing.

“If I identify a potential risk in a project, my first step is to assess the various factors that could lead to a poor outcome. Prevention requires analysis. Ensuring I fully understand what can trigger the undesired event creates the right foundation, allowing me to figure out how to reduce the likelihood of those events occurring. Once I have the right level of understanding, I come up with a mitigation plan. Exactly what this includes varies depending on the nature of the issue, though it usually involves various steps and checks designed to monitor the project as it progresses to spot paths that may make the problem more likely to happen. I find this approach effective as it combines knowledge and ongoing vigilance. That way, if the project begins to head into risky territory, I can correct its trajectory.”

17 More Problem-Solving-Based Interview Questions

In the world of problem-solving questions, some apply to a wide range of jobs, while others are more niche. For example, customer service reps and IT helpdesk professionals both encounter challenges, but not usually the same kind.

As a result, some of the questions in this list may be more relevant to certain careers than others. However, they all give you insights into what this kind of question looks like, making them worth reviewing.

Here are 17 more problem-solving interview questions you might face off against during your job search:

  • How would you describe your problem-solving skills?
  • Can you tell me about a time when you had to use creativity to deal with an obstacle?
  • Describe a time when you discovered an unmet customer need while assisting a customer and found a way to meet it.
  • If you were faced with an upset customer, how would you diffuse the situation?
  • Tell me about a time when you had to troubleshoot a complex issue.
  • Imagine you were overseeing a project and needed a particular item. You have two choices of vendors: one that can deliver on time but would be over budget, and one that’s under budget but would deliver one week later than you need it. How do you figure out which approach to use?
  • Your manager wants to upgrade a tool you regularly use for your job and wants your recommendation. How do you formulate one?
  • A supplier has said that an item you need for a project isn’t going to be delivered as scheduled, something that would cause your project to fall behind schedule. What do you do to try and keep the timeline on target?
  • Can you share an example of a moment where you encountered a unique problem you and your colleagues had never seen before? How did you figure out what to do?
  • Imagine you were scheduled to give a presentation with a colleague, and your colleague called in sick right before it was set to begin. What would you do?
  • If you are given two urgent tasks from different members of the leadership team, both with the same tight deadline, how do you choose which to tackle first?
  • Tell me about a time you and a colleague didn’t see eye-to-eye. How did you decide what to do?
  • Describe your troubleshooting process.
  • Tell me about a time where there was a problem that you weren’t able to solve. What happened?
  • In your opening, what skills or traits make a person an exceptional problem-solver?
  • When you face a problem that requires action, do you usually jump in or take a moment to carefully assess the situation?
  • When you encounter a new problem you’ve never seen before, what is the first step that you take?

Putting It All Together

At this point, you should have a solid idea of how to approach problem-solving interview questions. Use the tips above to your advantage. That way, you can thrive during your next interview.

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string interview questions problem solving

Co-Founder and CEO of TheInterviewGuys.com. Mike is a job interview and career expert and the head writer at TheInterviewGuys.com.

His advice and insights have been shared and featured by publications such as Forbes , Entrepreneur , CNBC and more as well as educational institutions such as the University of Michigan , Penn State , Northeastern and others.

Learn more about The Interview Guys on our About Us page .

About The Author

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Co-Founder and CEO of TheInterviewGuys.com. Mike is a job interview and career expert and the head writer at TheInterviewGuys.com. His advice and insights have been shared and featured by publications such as Forbes , Entrepreneur , CNBC and more as well as educational institutions such as the University of Michigan , Penn State , Northeastern and others. Learn more about The Interview Guys on our About Us page .

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Welcome to the daily solving of our PROBLEM OF THE DAY with Nitin Kaplas . We will discuss the entire problem step-by-step and work towards developing an optimized solution. This will not only help you brush up on your concepts of Tree but also build up problem-solving skills. In this problem, we are given an integer n, return the fibonacci series till the nth(0-based indexing) term. Since the terms can become very large return the terms modulo 10^9+7. Example :

Input: n = 5 Output: 0 1 1 2 3 5 Explanation: 0 1 1 2 3 5 is the Fibonacci series up to the 5th term. Give the problem a try before going through the video. All the best!!! Problem Link: https://www.geeksforgeeks.org/problems/fibonacci-series-up-to-nth-term/1

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  2. 10 problem-solving interview questions to find top talent

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COMMENTS

  1. 51 string interview questions (coding problems with solutions)

    Here's a quick list of string interview questions to get started with: String interview questions (5 typical examples): Given a string, create a new string without vowels and print that string. Given a string, create a new string with the same characters in a random order. Given a string containing some words in (possibly nested) parentheses ...

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    So all the techniques you know by solving array-based coding questions can be used to solve string programming questions as well. Here is my list of some of the frequently asked string coding ...

  4. Top 25 String Manipulation Interview Questions and Answers

    The first method is to use a for loop. Initialize a counter variable at zero, then iterate over each character in the string, incrementing the counter by one each time. At the end of the loop, the counter will hold the length of the string. The second method involves using the reduce function from the functools module.

  5. Top 21 String Programming and Coding Interview Questions With ...

    Since coding and problem solving are an important part of any programming job interview, it's imperative that you know how to solve them in time and in a pressure situation, which comes only after doing practice with the right set of questions. ... That's all about some frequently asked String Programming interview questions for preparing ...

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    This special behavior makes it one of the hottest topics in Java interviews. In this tutorial, we'll go through some of the most common interview questions about String. 2. String Fundamentals. This section consists of questions that concern the String internal structure and memory. Q1.

  7. Top 20 String Coding Problems from Programming Job Interviews

    A good thing about the string data structure is that if you know the array data structure, you can easily solve string-based problems because strings are nothing but a character array. So all the techniques you know by solving array-based coding questions can be used to solve string programming questions as well.

  8. Top String Coding Interview Questions

    String interview questions range from smooth string manipulation questions to more complex issues like string matching algorithms and regular expressions. Go through this guide to excel in string coding interview questions. This guide will be useful in building your proficiency in solving string-based problems.

  9. String Manipulation Interview Questions

    Interview Preparation Kit. String Manipulation. String Manipulation ... Alternating Characters . Easy Problem Solving (Basic) Max Score: 20 Success Rate: 97.45%. Solve Challenge. Sherlock and the Valid String. Medium Problem Solving (Basic) Max Score: 35 Success Rate: 66.02%. Solve Challenge. Special String Again. Medium Problem Solving ...

  10. String Cheatsheet for Coding Interview Prep

    Most string problems use the same problem-solving patterns that we talked about for arrays. Here are the question types you may encounter: In a lot of questions, you need to count the number of ...

  11. Top 20 String Algorithm Questions from Coding Interviews

    Each letter should have the same count in both strings. For example, the Army and Mary are an anagram of each other. 3) How to program to print first non repeated character from String? (One of the most common string interview questions: Find the first non-repeated (unique) character in a given string. for example, if given String is "Morning" then it should print "M".

  12. Java String Interview Questions

    Here are some FAQs related to Java String Interview Questions. 1. Why is string manipulation important in Java interviews? ... Answer: To stand out, demonstrate not only your knowledge of string manipulation but also your problem-solving skills. Be prepared to explain your thought process and how you arrive at solutions. Sharing examples of ...

  13. Top 30 Java String Interview Questions (2024)

    Java String Interview Questions for Experienced 16. Explain Character Encoding. What is the difference between UTF-8 and UTF-16? ... here is your go-to resource for practicing and evaluating your problem-solving skills. Enrol in this python basics guided path to master the basics of python, such as functions, loops, lists, strings, etc.

  14. Practice questions on Strings

    Practice questions on Strings. String is an important topic from GATE exam point of view. We will discuss key points on strings as well different types of questions based on that. There are two ways to store strings as character array (char p [20]) or a pointer pointing to a string (char* s = "string"), both of which can be accessed as arrays.

  15. The Technical Interview Guide to String Manipulation

    There are many ways to accomplish it. We can put the string in a Set, and then it is automatically split into characters. Since Set is an object to store unique values, its size should be the same as the string length if it is an isogram. The algorithm's time complexity is O (1), and space complexity is O (1).

  16. 50 String Coding Questions Using Python

    First, the code assigns the string '50 String Coding Questions Using Python' to the variable string1. Next, the startswith () method is used to determine if string1 starts with the substring ...

  17. 15 Common Problem-Solving Interview Questions

    Here are a few examples of technical problem-solving questions: 1. Mini-Max Sum. This well-known challenge, which asks the interviewee to find the maximum and minimum sum among an array of given numbers, is based on a basic but important programming concept called sorting, as well as integer overflow.

  18. Java String FAQs and Interview Questions

    Java String FAQs or Interview Questions. A list of top Java String FAQs (Frequently Asked Questions) or interview questions are given below. These questions can be asked by the interviewer. 1) How many objects will be created in the following code? String s1="javatpoint"; String s2="javatpoint";

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    Solve the most popular string & tries interview questions. Prepare for DSA interview rounds at the top companies. Solve the most popular string & tries interview questions. ... Problem Name. Score. Accuracy. Difficulty. Company. Reverse Words in String. 50. 73 % medium +6. Longest Palindrome in String. 50. 48 % medium. Roman Numeral to Integer ...

  20. 25+ JavaScript Coding Interview Questions (SOLVED with CODE)

    arrayList = []; console.log(anotherArrayList); // Output ['a', 'b', 'c', 'd', 'e', 'f'] Method 2. arrayList.length = 0; Above code will clear the existing array by setting its length to 0. This way of empty the array also update all the reference variable which pointing to the original array. This way of empty the array is useful when you want ...

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    MIKE'S TIP: When you're answering this question, quantify the details. This gives your answer critical context and scale, showcasing the degree of challenge and strength of the accomplishment. That way, your answer is powerful, compelling, and, above all, thorough. 2. Describe a time where you made a mistake.

  22. Top 50 Array Coding Problems for Interviews

    Find the first repeating element in an array of integers. Solve. Find the first non-repeating element in a given array of integers. Solve. Subarrays with equal 1s and 0s. Solve. Rearrange the array in alternating positive and negative items. Solve. Find if there is any subarray with a sum equal to zero.

  23. 8 Common Problem-Solving Interview Questions and Answers

    Problem-solving interview questions are questions that employers ask related to the candidate's ability to gather data, analyze a problem, weigh the pros and cons and reach a logical decision. Also known as analytical skills interview questions, these questions will often focus on specific instances when the candidate analyzed a situation or ...

  24. PROBLEM OF THE DAY : 23/03/2024

    We will discuss the entire problem step-by-step and work towards developing an optimized solution. This will not only help you brush up on your concepts of Tree but also build up problem-solving skills. In this problem, we are given an integer n, return the fibonacci series till the nth(0-based indexing) term.