Top Data Structure Interview Questions & Answers10 min read
Reading Time: 7 minutesHave you ever wondered, how data is stored and organized in the databases? It’s possible only due to the data structure. You can organize the data and make it available at any point in time. If you are looking to grab a job in the top productbased companies like Google, Microsoft, Amazon, Apple Inc, etc, you need to have a strong data structure foundation.
In this article, we will be discussing various data structure interview questions and answers to help you. In fact, these questions and answers will help you get an overview of the interview. If you can master the basics, there will be enough opportunity to land into your dream job.
This blog will help you get an insight into the data structure interview. Furthermore, we have tried to give you an overview from basics to advanced levels to make you feel comfortable during the interview.
In addition to this, we will give you a link to a brief overview of programmatic questions. They are also asked during the interview. To sum up, the main purpose of this blog is to guide you through every possible stage of data structure interview.
Also, find a list of C Programming Interview Questions and answers with programming examples for beginners and professionals.
Data Structure Interview Questions:

 Describe Data Structure.
 Explain how does a linear data structure differs from a nonlinear data structure?
 Tell us about various operations performed on the different data structures.
 Discuss how array varies from a linked list.
 Discuss the application of Stack.
 How does a POP operation differ from a PUSH operation?
 What is the basic difference between NULL and VOID?
 What is a queue and how is it different from the stack?
 How does a variable declaration affect memory allocation?
 Describe the types of linked lists.
 Discuss in detail about Binary Trees.
 How is a new item inserted in a binary search tree?
 List the types of trees.
 Which Data Structure suits most in tree construction?
 What are the advantages of Heap over Stack?
 What is Data Abstraction?
 How does a selection sort work for an array?
 How do signed and unsigned numbers affect memory?
 What are the dynamic data structures?
 What is a graph?
 Describe an AVL tree.
 How do you search for a target key in a linked list?
 What are the different Sort techniques in Data Structures?
 What is the difference between File Structure & Storage Structure?
 Which Data Structure is used in RDBMS, Network Data Model, Hierarchical Data Structure?
Data Structure Interview Questions and Answers:
The answers here will boost your preparation in addition to providing an overview.
1. Describe Data Structure?
Data Structure is a process to organize and manipulate data. In addition to this, it also describes the relationship between them. Furthermore, it is a central part of many computer science algorithms as programmers find it easy to handle data in an efficient way.
2. Explain how does a linear data structure differs from a nonlinear data structure?
If the elements of a data structure form a sequence or a linear list then it is called a linear data structure. On the other hand, nonlinear data structures are those in which the traversal of nodes is done in a nonlinear way.
Arrays, linked lists, stacks, and queues are examples of linear data structures, while graphs and trees are those of nonlinear data structures.
3. Tell us about various operations performed on different data structures?
The following operations are performed on different data structures.
Insertion
Deletion
Traversal
Searching
Sorting
Insertion is used to add a new data item whereas deletion is used to delete existing data from a given set. Similarly, traversal is used to access each data. Moreover, searching is used to find out the location of an existing data item in the set whereas sorting is used to arrange data in some order for its proper organization and usage.
4. Discuss how array varies from a linked list?
The array has a fixed size whereas the linked list varies in size. Moreover, arrays have better cache locality which makes a big difference in performance. In fact, linked lists don’t allow random access. However, one can easily perform insertion and deletion on a linked list whereas it is difficult in an array.
5. Discuss the application of Stack?
A stack is a linear data structure based on order LIFO (Last In First Out) or FILO (First In Last Out).
The basic operations carried out on Stack are Push, Pop & Peek.
Application of Stack:
a. Infix to postfix conversion.
b. Reverse a String.
c. Implement two stacks an array
d. Check for balanced parentheses in an expression
6. How does a POP operation differ from a PUSH operation?
Both PUSH and POP operations concern a stack. Data is added to the stack using the PUSH operation, while it is recovered using the POP operation.
7. What is the basic difference between NULL and VOID?
While NULL is a value, VOID is a type of data identifier. A variable assigned with a NULL value represents an empty value. The VOID is used for identifying pointers that have no initial size.
8. What is a queue and how is it different from the stack?
A queue is a kind of linear structure that follows the First In First Out approach for locating elements. Dequeue, enqueue, front, and rear are basic operations on a queue. Like a stack, a queue can be implemented using arrays and linked lists.
However, in a stack, the item that is most recently added is eliminated first. Contrary to this, the item least recently added is eliminated first in case of a queue.
9. How does a variable declaration affect memory allocation?
The total amount of memory to be allocated in the case of a variable declaration depends solely on the data type used. For instance, declaring an integer type variable reserves 4 bytes of memory space while declaring a double variable saves 8 bytes of the available memory.
10. Describe the types of linked lists?
The linked list is a linear data structure where every element is a separate object.
You may also like to watch the complete video on Data Structure Interview Questions:
Linked list Types:
a. Single linked lists:
Every node stores address or reference of the next node in the list. Similarly, the last node has the next address or reference.
b. Doubly linked lists
There are two references associated with each node. One reference points to the next node whereas the other one points to the previous one.
c. Circular linked lists
Here all nodes are connected to form a circle. In fact, there is no NULL at the end. egs: 1>2>3>1 [The next pointer of the last node is pointing to the first].
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11. Discuss in detail about Binary Trees?
It is a finite set of elements that is either empty or further divided into subtrees. In other words, it is also called a nonlinear data structure. One can call the child node on left as ‘left child node’ whereas the child node on right as ‘right child node’.
There are three types of Binary Trees:
a. Full binary tree
b. Complete binary tree
c. Threaded binary tree
12. How is a new item inserted in a binary search tree?
Since a binary search tree does not allow duplication, the new item to be inserted must be unique. Then we will proceed with checking whether the tree is empty or not. If it is empty, then the new item will be inserted in the root node.
However, if the tree is not empty, we will refer to the key of the new item. When it is smaller than the root item’s key, the new item will be added to the left subtree. If the new item’s key is greater than the root item’s key, then the new item is inserted into the right subtree.
13. List the types of trees?
Given below is the list of the types of trees:
a. General Tree
b. Binary Tree
c. Binary Search Tree
d. Expression Tree
14. Which Data Structure suits most in tree construction?
Queue data structure suits most in tree construction
15. What are the advantages of Heap over Stack?
Heap is more flexible than stack. Furthermore, it is durable than the stack. However, Stack allocates memory very fast than the heap. There is a dynamic allocation of memory for the heap.
16. What is Data Abstraction?
Data abstraction is a process to break down complex data problems into manageable chunks. This helps in better operation and storage of data.
17. How does a selection sort work for an array?
Here, subscript zero contains the smallest element. In other words, the smallest element gets the first position. Similarly, the second smallest elements get the second position and so on.
18. How do signed and unsigned numbers affect memory?
A signed 8‑bit number has a range of (0–255) whereas an unsigned 8‑bit number has a range of ‑128 to 127. Similarly, the Unsigned 8‑bit number has all the bits available.
19. What are the dynamic data structures?
When a program runs, the dynamic data structures expand and contract. In other words, it can adjust as per the size of the data.
20. What is a graph?
A graph is a nonlinear data structure that contains nodes and edges.
Graphs are used to represent networks which include path in a city or telephone networks, etc. Similarly, they are used in social networks like Linked In, Facebook or Twitter, etc.
21. Describe an AVL tree?
AVL tree is used to balance the existing binary search tree. In fact, it is always in a partially balanced state.
22. How do you search for a target key in a linked list?
You can search for a target key using a sequential search in a linked list. Firstly, each node is traversed and compared with the target key. Then, the different one follows the link to the next node.
23. What are the different Sort techniques in Data Structures?
The different types of sort techniques in data structures are listed below:
a. Buble sort
b. Selection sort
c. Merge sort
d. Insertion sort
e. Quicksort
f. Heapsort
Data Structure Interview Questions and Answers on Files and Databases:
24. What is the difference between File Structure & Storage Structure?
File Structure:
If you write a data in the file and save that file in the hard disk or any other external device, the data will remain intact until it is deleted manually. To sum up, this act of saving data in a file on an auxiliary memory is called a file structure.
Storage Structure:
Every variable and constants have memory allocated in the main memory called a storage structure.
25. Which Data Structure is used in RDBMS, Network Data Model, Hierarchical Data Structure?
RDBMS uses an array data structure whereas Network Data Model uses graph and Hierarchical Data Structure uses tree data structures.
Data Structure is the most important topic in computer science. Almost all the product based companies that pay you a higher salary expect you to be proficient in it. To sum up, you have to give more time.
In fact, a data structure is the foundation of every programming language and software, as well as, hardware. Hence, if you can master it, cracking the data structure interview will be a piece of cake.
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