Data Structure Interview Questions

Data structures and algorithms form a crucial component of any programming interview. Data structure interview questions are also asked at data science and Java interviews.

Data Structure Interview Questions

To help you crack your next programming interview we have listed some of the important data structure interview questions.

1. What are data structures?

Ans. Data structures are a way of organizing and representing information. Just as we use a type variable array to represent a finite number of elements, we can represent a list in a data structure. Data structures have an internal behavior and are governed by certain rules/restrictions.

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2. What are the types of data structures?

Ans. There are two types of data structures –

Linear Data Structures – The linear data structures are the ones where all the elements are arranged sequentially, precisely, and one after another. These elements are arranged in a particular order and are easy to implement.

Non-linear Data Structures – In non-linear data structures, elements are usually not in any particular sequence. Instead, the arrangement is hierarchical, where elements are connected to one or more elements.

To understand the type of data structures, this infographic can be helpful –

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3. What is the difference between linear and non-linear data structures?

Ans. This is one of the most commonly asked data structure interview questions –

Linear Data Structures	Non-Linear Data Structures
Data items are arranged in a sequential order	Data items are arranged in non-sequential order
Data items are present on the single layer	Data items are present at different layers
Allows traversal of all the data elements in a single pass, sequentially	Not possible to traverse all the data elements in a single pass
Less efficient memory utilization	Efficient ways of memory utilization basis applications
Time complexity goes up with an increase in data size	Time complexity doesn’t change
Examples include – Array, Queue, Stack, Linked List, etc.	Examples include – Tree and Graph
Easy to implement	Implementation is complex

4. Why are data structures important?

Ans. Data structures are important because they are tools that can be used to organize information in the digital space and solve complex data problems. They help to keep the codes relatively simple, and also make codes run faster. Since data structures are a crucial element in data science and computer science, it has now found their way into fields like Artificial Intelligence, deep learning, machine learning, neural networks, operating systems, graphics, etc.

5. Which data structure type would you choose?

Ans. The choice of one of these data structures will depend on the type of application that you want to carry out.

6. What are the applications of Data Structures?

Ans. Applicability of data structures is diverse, some of which include –

Data Structure	Application
Array	Mobile phone contacts
Linked List	Next feature in music players
Trees	Databases indexing
Stacks	Undo and Redo tasks in editors
Queues	Operating Systems to schedule FCFS
Graphs	LinkedIn, Google Maps, and Facebook

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7. What are the types of linear data structures?

Ans. There are mainly 4 types of linear data structures –

Array – An array is a finite and ordered set of homogeneous elements. Its ordered condition makes it possible to identify all the elements existing in the data structure. Because of its homogeneous nature, it indicates that its elements are composed of the same type of data. Arrays can vary according to the programming language, but the important thing is that, in any language, an array is a data structure that stores a set of values ​​that belong to the same data type.

Queue – A queue is a type of linear structure similar to stacks, differing from them in the way of inserting/eliminating elements. In this case, deletions are made at the beginning of the row, while insertions are made at the other end, that is, the end. The queues in the data structure have a mechanism known as FIFO (first-in, first-out). Queues are used to store data that needs to be processed on a first-come, first-served basis.

Stack – Stack refers to a special type of linear data structure in which the insertion and deletion of new elements are done only at one end, mainly top of the stack. It is based on LILO (last-in, first-out) mechanism, in which the last element that is put on the stack is the first none to be taken out. 

Linked List – Linked Lists are made with elements or data structures, located one after another in sequence. Each element is connected to the next through a link. Its operations depend on the need of the application and do not follow a specific mechanism. A linked list is defined by three points:

• The information contained in its elements and their respective links
• The link that allows access to the first item in the list
• A means of detecting the last item in the list

8. What are the types of non-linear data structures?

Ans. There are two types of nonlinear data structures –

Tree – The trees in the data structure are a nonlinear structure used to represent data with a ratio hierarchical in that each element has a unique predecessor, and can have multiple successors.

Graphs – The graphs in the data structure are other non-linear structures and trees.

9. What is the difference between file structure and storage structure?

Ans. The main difference between file structure and storage structure is based on the memory area being accessed

Storage structure – The representation of the data structure in the memory of a computer is its storage structure

File structure – The representation of data storage structure in the auxiliary memory

10. What is a multidimensional array?

Ans. A multidimensional array is one with more than one dimension and has numerous layers. The 2D array is the basic multidimensional array and is regarded as a matrix or a table with rows and columns. In a 2D array, each element is associated with two indexes.

11. What are the common operations on various data structures?

Ans. We can perform different types of operations in data structures, such as –

Insert – We can insert a new data item in a data structure
Search – We can find an element in the data structure
Sort – We can perform simple data sorting, like arranging values in increasing or decreasing orders
Delete – We can remove unwanted data points in a data structure
Traversal – We can access every data item once for further processing

12. What types of searching is used in Data Structures?

Ans – Below are the different types of searches in data structure –

• Linear Search
• Binary Search
• Jump Search
• Interpolation Search
• Exponential Search

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