36 Famous Data Structures Interview Questions and Answers!

Famous Data Structures Interview Questions and Answers

If you’re looking for a position in programming, coding, or software development, you should be prepared to answer data structure and algorithm questions in an interview. Reviewing common questions can help you prepare a thorough and detailed answer that will impress the hiring manager. In this article, we’ll look at common algorithm and data structure interview questions and provide sample answers to help you prepare for your next interview.

Interview Questions about Experience and Background

These common questions are designed to elicit information about your specific knowledge and skills:

  1. How did you learn to code?
  2. Where did you go to college?
  3. What was your major?
  4. What is your highest level of education?
  5. How long have you been working in programming?
  6. How did your last position prepare you for this role?
  7. Did your last position involve data structures?
  8. Do you like working in a team?
  9. Will you be able to explain data structures to colleagues who are not familiar with programming?
  10. Have you held a leadership role before?

Interview Questions about General Data Structures

Your replies to these general questions will display to the interviewer that you recognize how data structures work.

  1. What is a data structure?
  2. What is a field?
  3. What is a multidimensional array?
  4. What is a linked list data structure?
  5. What is a recursive data structure?
  6. What is string encoding?
  7. What is a binary tree?
  8. What is a merging species?
  9. What is the difference between “null” and “void?”
  10. What is the dissimilarity among “push” and “pop?”
  11. What is data abstraction?
  12. What is a postfix expression?
  13. What are the major benefits of data structure?
  14. What is a dequeue?
  15. What is the Huffman algorithm?
  16. How many queues do you need to perform a priority queue?

Interview Questions Algorithm and Data Structure

Here are common algorithm and data structure interview questions with explanations and sample answers.

1. Where should you use data structures?

Your answer will demonstrate that you understand what the interviewing company is doing. Demonstrate that you will be able to structure their data appropriately by referencing company-specific elements.

Example: “Data structures can be effectively applied anywhere data exists. However, it is most useful in database management, number analysis, graphics, and compiler design.”

2. How would you remove duplicates from a given array in Java?

An array is a structure that most programming languages ​​use to implement other data structures such as strings, stacks, queues, and lists. Since this is a basic data structure, you may encounter several different field-related questions during the interview process. To successfully answer this Java array question, you should have a basic understanding of Java and how to apply constructors such as recursion and loops.

Example: “I can describe two ways you can do this. First, you can use an iterator. To do so, you must create a new ArrayList. You then need to loop through the original ArrayList that contains the duplicate values ​​and store the first occurrence of each element in the new ArrayList using the contains() method. The second ArrayList will contain all the elements of the original array minus the duplicate elements.

The second and better way you can remove duplicates from an array is to create a LinkedHashSet from the original ArrayList, which will automatically remove duplicates because the latter doesn’t allow it. The LinkedHasSet should be converted back to an ArrayList, which will then contain all the elements with the duplicates removed.”

3. When should you use binary search?

A hiring manager may ask a similar question to gauge your decision-making skills. Answer confidently and provide a real-life example applicable to the hiring company.

Example: “You can practice the binary search algorithm with an organized and fixed list of elements. The search will start in the middle of the list and from there it will determine whether to continue searching at the top or the bottom.”

4. How would you identify and eliminate a loop in a linked list?

An associated list is a data structure that, similar to an array, is linear. However, while arrays store their elements in contiguous locations, linked lists store elements randomly and link them using pointers. In general, a linked list is a data structure made of nodes, each of which consists of a data field and a link that points to the next node in the list. Loops in a linked list can cause program errors. To answer this question well, you should have a good understanding of recursion as it is a recursive data structure.

Example: “To detect and remove a loop in a linked list, you should write a detectAndRemoveLoop function that checks for a loop in the linked list and then removes it if it is present, then returns true. If no loop is identified, the function yields false.

5. Given an integer “n”, write a function to calculate the nth Fibonacci number.

Dynamic programming involves dividing a complex problem into simpler subproblems and storing the solution to each subproblem. This way, the programmer does not have to recalculate the solution. Using the Fibonacci sequence can reduce the running time of the program. To answer this question you should be comfortable with algorithms and coding as there are many different methods to write this sequence.


“public long Fibonacci(int x) {

if (x < 0) return – 1;

if (x == 0) return 0;

long[] cache = new long[x + 1];

for (int i = 1; i < cache.length; i++) {cache[i] = -1;}

cache[1] = 1;

return Fibonacci(x, cache);


private long fibonacci(int x, long[] cache) {

if (cache[x] > -1) return cache[x];

cache[x] = fibonacci(x – 1, cache) + fibonacci(x – 2, cache);

return cache[x];


6. How do you implement postorder tree traversal recursion?

A binary tree is a data structure that, unlike arrays and linked lists, does not store elements linearly, but hierarchically. These binary tree questions test your ability to evaluate or eliminate an expression. To answer this question, you should be able to visually show how to create a postorder recursion so that the hiring manager can see your process.

Example: “A traversal of a tree next assembling node ‘n’ contains the ensuing stages, beginning from the root:

• The false subtree of n is traversed by calling printPostorder(n.left).

• The true subtree of n is traversed by calling printPostorder(n.right).

• After that, node n itself is visited.”

7. How do you find that two integers have opposite signs?

Bit manipulation allows the programmer to work with bits as opposed to the abstractions used in modern programming languages. They typically use this kind of programming to detect and fix algorithms, low-level device control, data compression, optimization, and encryption algorithms. Bitwise manipulation uses bitwise operations, which is a level of operations that work with individual bits, which are the smallest units of data. To answer questions about bit manipulation, you should be familiar with bitwise operations.

Example: “When two integers have opposite signs, it means that their most significant bits are different. The most significant bit of any negative number will always be one, while the most significant bit for positive numbers will always be zero. If you apply the bitwise exclusive OR operator (XOR “^”) to two integers with opposite signs, you get a negative number. This refers that if the XOR operator is engaged to two integers and returns less than zero, the two numbers have contradictory signs.

When you attend an interview that might include questions about programming, consider bringing a notepad and writing utensil so you can offer visual responses. The interview space may have a whiteboard where you can write lines of code, but you should go to the interview prepared with your own writing supplies.

8. What kind of data structure allows you to easily manipulate the elements in a linked list?

Your answer will show the interviewer that you understand the different forms of data structures. It will also demonstrate your ability to solve problems, prioritize and make quick decisions.

Example: “The best data structure to use if you want to move the elements of a linked list is a linked list structure. Instead of creating an array, you just change the list.”

9. Explain the difference between an array and a stack.

Your answer will demonstrate the ease with which you can discuss common data structure terms. If possible, please add an example of how the differences between array and stack might apply to the inquiring company.

Example: “Shells and arrays store data in two different ways. First, it is a data type. Stacks can stock diverse types of data, while arrays stock data of the identical type. Second, there is the size of the structure. Stacks differ in size as elements are detached or added. The size of the fields does not change.

10. Clarify the change among a linear data structure and a hierarchical data structure.

Your reply should validate your awareness of basic data structure. It will also show the hiring manager that you can clearly explain programming terms and ideas.

Example: “Linear data structures and hierarchical data structures define the associations among pieces of data, but vary in how the data act together. Linear data structures organize data in a one-level sequence. Hierarchical data structures manage data in a multi-level pattern.”

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