Top Data Structure Interview Questions With Example Answers

By Indeed Editorial Team

Updated 30 July 2022

Published 12 June 2021

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Preparing for a job interview usually involves a lot of research and practice. Reviewing and practising common interview questions for a particular position can make you feel confident during the interview. If the position that you are interviewing for uses data structures, you might be interested in some common interview questions that recruiters can ask you. In this article, we will list some of the top data structure interview questions, along with some example answers and explanations to help you prepare for your interview.

General Interview Questions On Data Structures

Below are some of the most common interview questions on data structures. Your answers to these questions will tell the interviewer about your understanding of how data structures work:

  • What is a data structure?

  • How many types of data structures are there?

  • What are the major applications of data structures?

  • Where are data structures used?

  • What is an array?

  • What is a multi-dimensional array?

  • What is a stack?

  • What is a linked-list data structure?

  • Are linked-list data structures linear or non-linear?

  • What is a recursive data structure?

  • Are linked-list data structures more efficient than arrays?

  • What is a queue?

  • What are binary trees?

  • What is LIFO?

  • What is FIFO?

  • What is string coding?

  • What is the difference between NULL and VOID?

  • What do you mean by linear search?

  • What is the difference between PUSH and POP?

  • What are dynamic data structures?

  • What do you mean by data abstraction?

  • What is a dequeue?

  • Explain the difference between a stack and a queue.

  • What is Huffman's algorithm?

  • What is a postfix expression?

Related: How to Succeed in Your First Interview

Questions Regarding Your Background And Experience

Questions regarding your previous experience and background will help the interviewers to know if you have developed the specific knowledge and skills required for the job. Some common questions that recruiters can ask you in your interview include:

  • What was your major in college?

  • How much experience do you have working on data structures?

  • How would you rate yourself on data structures?

  • What is your highest qualification?

  • How did you learn to code?

  • How much experience do you have in programming?

  • Did you use data structures in your previous role?

  • What experience in data structures will you bring if you join us?

  • How comfortable are you working with a team?

  • Do you prefer working as an individual contributor or as a team member?

  • Have you led a team in your past experience?

  • Why are you looking for a change?

  • Will you be able to guide your juniors who are not well-versed in data structures?

  • Tell me about a situation where you got an appreciation for your work.

  • Tell me about a situation where you could deliver something within a tight deadline.

  • How did your previous experience prepare you for this role at this organisation?

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In-Depth Questions

Most of the positions that use data structures will not only need your knowledge of programming and understanding of data structures but will also need problem-solving skills and critical thinking. Some questions that interviewers may ask to judge your problem-solving and critical thinking include:

  • Why are data structures used and what purpose do they serve?

  • If you want to implement LRU cache, which data structure will you choose?

  • Without using a temporary variable, how can you trade two integers?

  • Is heap better than a stack? Why or why not?

  • Which is the fastest algorithm that you can use for sorting?

  • Can you explain the working of a recursive algorithm?

  • How would you go about designing a vending machine?

  • What are linked lists? Are they binary or non-binary data structures? Why?

  • How can you reverse a linked list?

  • How can you find duplicate characters in a string?

  • How can you search for a target key in a linked list?

  • Can you explain the working of the selection sort?

  • How can you find the largest or the smallest integer in an unsorted integer array?

Related: How to Prepare for a Job Interview

Interview Questions With Sample Answers

Below we have collated some of the most common data structure interview questions with explanations and example answers:

What kind of data structure can help you to easily manipulate elements in a connected list?

The purpose of this question is to get an idea of your understanding of multiple forms of data structures. This question will also test your problem-solving skills and how you prioritise and make quick decisions.

Example: "Linked-list data structure is the best data structure to use if we want to manipulate elements in a connected list. Just changing the list rather than creating an array will do the job."

What is the difference between a linear data structure and a hierarchical data structure?

By asking this question, the interviewer will not only judge whether you have a good understanding of data structures or not but will also be able to figure out if you can express your programming terms and ideas clearly.

Example: "Linear data structures and hierarchical data structures both describe the relationships between pieces of data, but they differ in how the data interacts. While linear data structures organise data in a single-level sequence, hierarchical data structures organise data in a multi-level configuration."

In what circumstances should you apply a binary search?

This question will help the interviewer determine your decision-making skills. It would be best if you could answer this question by providing a real-life example, preferably relevant to the company and the industry you are interviewing for.

Example: "Binary search algorithm can be used with a list of ordered and sorted elements. This search works by repeatedly dividing the search interval in half. The search starts in the middle of the list and then determines from there whether to continue the search at the top end or the bottom end based on the value returned. This is checked repeatedly until the value is found."

Where should you use data structures?

Your answer to this question will help the interviewer evaluate your understanding of what the interviewing company does. Your answer should be specific to the interviewing company, and you should be able to demonstrate how you can appropriately structure their data by referencing elements specific to the company.

Example: "Though data structures are most useful in database management, data analysis, graphics and compiler design, these can be used and applied effectively anywhere data exists."

What do you mean by bubble sort and how do you use it?

The answer to this question will help the interviewers in judging your knowledge of data structures and help them understand the depth of your knowledge. It will also demonstrate your critical thinking skills to the interviewers.

Example: "A bubble sort is a sorting technique that can be applied to data structures, such as an array. The working of this sorting technique is simple, and it works by comparing the adjacent values of the array and exchanging them if they are out of order. In this way, the smaller values “bubble” to the top, while the larger values go down to the bottom."

What is the difference between a stack and an array?

Your answer to this question will give interviewers a perspective of your knowledge and your ability to discuss common data structure terms. You can add value to your answer by adding an example of how the differences between an array and a stack might apply to the interviewing company.

Example: "There are some fundamental differences in the way stacks and arrays store data. Arrays can store the same type of data, while stacks can store different types of data. There is also a difference in the size of the structure of stacks and arrays. Stacks change in size as elements are removed or added. Arrays do not change in size."

What operations can be performed on data structures?

This question will test your in-depth understanding of data structures and will give you an opportunity to demonstrate your high-level thinking on the subject. You should explain different operations that you can perform on data structures and should try to give an example relevant to the interviewing company, if possible.

Example: "Various operations that can be performed on a data structure are insertion, deletion, traversal, searching and sorting. Insertion is adding a new piece of data to the data collection. Deletion is removing a piece of data from the collection. The traversal operation is providing one-time access to a piece of data for processing. Searching is finding if a specific piece of data is within the given collection of data. Sorting is the arrangement of data, for example, in numerical or alphabetical order"

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