20 Data Structure Interview Questions for Freshers - TCS, Accenture, Infosys, Wipro,Cognizant,Amazon

Summary

In this video, Nishant explains various data structure interview questions and answers aimed at freshers. Key topics covered include the basics of arrays, linked lists, stacks, queues, trees, and graphs. He explains concepts like multi-dimensional arrays, doubly linked lists, and binary search trees, highlighting their characteristics, advantages, and real-world applications. Nishant also goes into basic operations of data structures such as push, pop, enqueue, and dequeue, as well as tree traversal methods like depth-first and breadth-first search. The video serves as a comprehensive guide for understanding fundamental data structures for interview preparation.

Takeaways

• 😀 Data structures are essential for organizing and storing data efficiently in memory, categorized into linear and non-linear structures.
• 😀 Arrays are static, linear data structures that store elements of the same type sequentially in memory, with fixed size.
• 😀 Multi-dimensional arrays, such as 2D and 3D arrays, allow storing arrays within arrays, useful for tabular or matrix-like data.
• 😀 Linked lists are dynamic, linear data structures consisting of nodes with data and pointers to the next node, offering efficient insertion and deletion.
• 😀 Doubly linked lists contain nodes with two pointers: one to the next node and one to the previous node, allowing bi-directional traversal.
• 😀 Stacks follow the LIFO (Last In, First Out) principle, with operations such as push, pop, and peak, and are useful in operations like string reversal.
• 😀 Queues follow the FIFO (First In, First Out) principle, with operations like enqueue, dequeue, and checking front/rear elements, often used in task scheduling.
• 😀 Trees are non-linear data structures that store data in a hierarchical format, allowing efficient access and management of data.
• 😀 Binary Search Trees (BSTs) maintain sorted order by ensuring each node’s left child is smaller and the right child is larger, aiding fast searching.
• 😀 Tree traversal methods like inorder, preorder, postorder, and breadth-first traversal help in systematically visiting nodes in a tree structure.

Q & A

What is a data structure?

A data structure is a way to store and organize data in the main memory so that it can be accessed and modified efficiently. Data structures are classified into linear and non-linear categories.

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

In linear data structures, the elements are arranged sequentially, where each element is connected to the element before and after it (e.g., arrays, stacks, queues, linked lists). In non-linear data structures, the elements are not arranged in a sequential manner, such as in trees and graphs.

How does an array work?

An array is a collection of data items of the same type, stored sequentially in memory. Arrays are static, meaning their size is fixed. Each element is accessed using its index.

What is a multi-dimensional array?

A multi-dimensional array is an array of arrays. For example, a 2D array stores data in a tabular format with rows and columns, while a 3D array stores multiple 2D arrays (tables).

What is the primary advantage of a linked list over an array?

The main advantage of a linked list over an array is its dynamic nature. Unlike arrays, which have a fixed size, linked lists can grow or shrink as needed without wasting memory.

What is a doubly linked list and its advantages over a singly linked list?

A doubly linked list contains an extra pointer that points to the previous node, allowing traversal in both directions. This makes operations like deletion more efficient, as there’s no need to traverse the list from the beginning to delete a node, unlike in singly linked lists.

What are the key differences between a stack and a queue?

A stack follows the LIFO (Last In, First Out) principle, where the last element inserted is the first to be removed. A queue follows the FIFO (First In, First Out) principle, where the first element inserted is the first to be removed.

What is a tree data structure and why is it considered non-linear?

A tree is a hierarchical data structure made up of nodes connected by edges. It is considered non-linear because the data is not stored in a sequential manner, and nodes are organized in a hierarchy.

What is a binary search tree (BST) and how does it improve search efficiency?

A binary search tree is a binary tree where each node’s left child is smaller than its parent, and the right child is larger. This structure allows for efficient searching, insertion, and deletion, as the search can be narrowed down at each step by comparing values.

What are the differences between directed and undirected graphs?

In a directed graph, edges have a direction, meaning they represent a one-way relationship between vertices. In an undirected graph, edges do not have a direction, meaning they represent a two-way relationship, and traversal can happen in both directions.