15 Data Structure And Algorithm Interview Questions To Practice Before Your Interview

Data Structure Interview Questions

Why Data Structures Are Important In Your Coding Career?

Here’s an example! Let’s assume you need to find your roll number in a printed document consisting of 100,000 pages where roll numbers are arranged in ascending order. If you try to search sequentially, that will be frustrating, right? Else you can pick a random page, let’s say page no. 12,500. If your roll number isn’t there but all other roll numbers are lesser than yours, then go to page no. 17,500. Still, if you don’t find your roll number, but this time, every other roll number is greater than yours, then go to page no. 15,000 and keep repeating this process until you find yours. Yes, this is one of the data structure interview questions.

Congrats, you just unintentionally used the Binary Search Algorithm!

With this example, it’s pretty safe to say that you have understood why data structures are so much important in computer programming and some Interview questions for the data structure. Not just key to cracking Interview questions data structures and algorithms in your software development career, but algorithms and data structures let you solve complex day-to-day problems in a short amount of time, that too, with fewer resources.

Now that you know why data structures are so important in computer science and programming, let’s look at a few common data structure interview questions that would guarantee a breeze-through in every round.

Question 1: Briefly explain your understanding of Data Structures.

Answer: In computer science, a Data Structure defines how to organize, interpret and manipulate data. Added specified algorithms, it also specifies the relationship between data. A few notable examples of Data Structures are arrays, Linked List, Queue, Stack, etc, enabling programmers to collect, interpret and manage data in an efficient manner.

Question 2: Describe the two primary types of Data Structures.

Answer: Data Structures are fundamentally classified into two types:

Two Primary types of data structure

Linear Data Structure: In Linear Data Structures, each element is arranged in a sequential order where datasets are stored non-hierarchically with each item having its successors and predecessors except the first and last element.

Non-Linear Data Structure: In Non-Linear Data Structure, the elements aren’t needed to be arranged in sequential order. This allows each item or element in the set to be connected to two or more items in a non-linear arrangement.

Question 3: What is the fundamental difference between file structure and storage structure.

Answer: The primary difference between file structure and storage structure is based on the accessed memory area. Storage Structure represents the entire data structure in the memory of a computer. Whereas, File Structure is the representation of the storage structure in the auxiliary memory (used for storing inactive programs and archives).

Question 4: Define Stack and its function.

Answer: In Data Structure, Stack is a sequential list where insertions and deletions can be executed only at the top end. Stacks can also be defined as a recursive data structure having a pointer to its top element and is often referred to as Last-in-First-out (LIFO), where an element inserted first in the stack will be deleted from the stack at the very last.

Question 5: Briefly explain your understanding of PUSH and POP.

Answer: PUSH and POP operations in Data Structure define how data is inserted and retrieved from the Stack. PUSH specifies that a particular data is inserted into the Stack and PULL denotes its retrieval or deletion from the Stack. The same terminology can also be observed in GitHub, a cloud-based Git repository to assist in coding collaboration.

Question 6: Define a multidimensional array?

Answer: Multidimensional arrays in a Data Structure is a niche feature that enables the creation of multiple arrays with numerous layers. The 2D array, also referred to as a matrix, is the fundamental form of a multidimensional array which requires the programmer to declare in C whether a multidimensional array is one-dimensional or two-dimensional.

Question 7: What do you understand by a linked list data structure?

Answer: In a linked list data structure, elements aren’t stored in adjacent memory locations. Rather, elements are linked using pointers to form a chain where every element is a discrete object, or a node. Each node has two items; a data field and a reference to the next node, making it a dynamic structure capable of growing and shrinking when needed.

[Linked List is one of the fairly common Data Structure Interview Questions. So, try to elaborate your answer to this question as much as possible with good examples, rather than ending your answer in one sentence]

Question 8: What type of data structure are Linked Lists; linear or non-linear?

Answer: Linked List Data Structures can be specified both in linear and non-linear Data Structures, depending upon their applications and intended use. If a Linked List is used for accessing strategies, it should usually be considered a linear structure, whereas, in storage applications, Linked Lists can also be considered as a non-linear Data Structure.

Question 9: Explain doubly-linked lists with an example.

Answer: Doubly-Linked is a complex double-ended liked list where every node has two links; a standard reference to the next node and another that connects to the preceding node. Doubly-Linked lists enable traversal across the data elements in both directions with a notable example being the browser cache with backward-forward visited pages.

Question 10: What is the process of referencing every element in a one-dimensional array?

Answer: To reference every element on a one-dimensional array, an index loop is used to access information, in which the counter counts from 0 to the maximum array in size, n, minus one. This counter is used as an array subscript for referring to every item in a one-dimensional array in sequence. By default, array indexing will always start from 0.

Let’s check out some more data structure interview questions that can help you to ace your tech interview.

Question 11: Explain the importance of doing an algorithm analysis.

why algorithm analysis is important - data structure interview question

Answer: An algorithm, which defines a set of functions to be executed in a certain sequence, is a step-by-step process of manipulating data to solve a given problem. However, a problem can be solved in multiple ways using different algorithms, which may yield varying results in certain cases. Therefore, algorithm analysis provides an estimation of required resources by quantifying the complexity of the problem. The time complexity specifies the amount of time to be required to solve a given query, whereas, space complexity specifies the amount of memory to be required.

Question 12: Define a Queue and what makes it different from a Stack.

Answer: The Queue is a linear data structure built around the fundamental of First-in-First-Out (FIFO) to access elements in a given data structure. The most notable and basic operations in Queue are Enqueue, Dequeue, Front, and Rear.

The primary difference between Stack and Queue is signified based on how an item is removed. In a Queue, only the least recently added element can be removed, whereas, in Stack, we remove the element most recently added.

Question 13: How to ensure if a given Binary Tree is BST or not?

Answer: A given Binary Tree is BST if in order traversal of the Binary Tree is sorted. Ensuring whether a Binary Tree is BST or not is as simple as to do in order traversal and while traversing keep track of the previous key values. For every node in the Binary Tree, a check is the maximum value in the left subtree is smaller than the node, else returns false.

Question 14: How does binary search work?

Answer: Binary search involves manipulating the already ordered data in a data structure, and is used when the primary criterion is efficiency. The first step is to find out the middle element of an array and the search begins from there. Then the array is searched in two parts depending on whether the value is higher or lower than the middle element.

Question 15: Briefly explain dynamic memory management in a data structure.

Answer: In dynamic memory management, storage units are constantly allocated depending on the requirements, where individual data structures can either be stored separately or combined to form entities, also known as composites. Dynamic memory is controlled by a program during its execution to ask for or delete additionally allocated memory.


Our freshly compiled data structure interview questions and answers will give you an insight into what questions could be asked in a data structure interview. Good coding skills and even the mastery of programming tools are incomplete with the fundamental knowledge of data structures, therefore, having a well-structured answer to every Data Structures and Algorithms Interview Questions can help you ace any highest paying job in India interview you are appearing for.

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