In the competitive landscape of technical interviews, mastering Data Structures and Algorithms (DSA) is crucial. Recruiters often focus on a candidate’s problem-solving skills and ability to think critically. To help you prepare, we’ve compiled a list of 40 commonly asked DSA questions, categorized for your convenience.

## Arrays and Strings

**Find the Maximum Sum Subarray**: Identify the contiguous subarray within a one-dimensional array that has the largest sum.**Find All Substrings that are Palindromes**: Write a program to list all the substrings of a given string that are palindromic.**Implement the “Two Sum” Problem**: Given an array of integers, return indices of the two numbers such that they add up to a specific target.**Implement Kadane’s Algorithm for Maximum Subarray Sum**: Use this algorithm to find the maximum sum of a contiguous subarray in an array.**Find the Missing Number in an Array of Integers**: In a given range, determine the missing integer in the array.**Merge Two Sorted Arrays into One Sorted Array**: Combine two sorted arrays while maintaining the sorted order.**Check if a String is a Palindrome**: Create a function to determine if a string reads the same forwards and backwards.**Find the First Non-Repeating Character in a String**: Identify the first character in a string that does not repeat.**Write a Program to Remove Duplicates from a Sorted Array**: Eliminate duplicates from a sorted array in-place.

## Linked Lists

**Reverse a Linked List**: Write a function to reverse a singly linked list.**Detect a Cycle in a Linked List**: Determine if a linked list contains a cycle.**Find the Middle of a Linked List**: Identify the middle node of a linked list.**Merge Two Sorted Linked Lists**: Combine two sorted linked lists into one sorted linked list.**Implement a Stack Using Linked List**: Create a stack data structure using a linked list.**Find the Intersection Point of Two Linked Lists**: Identify the node at which two linked lists intersect.

## Stacks and Queues

**Implement a Stack Using an Array**: Design a stack data structure with an array.**Implement a Stack that Supports Push, Pop, Top, and Retrieving the Minimum Element**: Enhance stack functionality with additional operations.**Implement a Circular Queue**: Design a queue that wraps around to the beginning when it reaches the end.**Design a Max Stack**: Create a stack that supports retrieving the maximum element in constant time.**Design a Queue Using Stacks**: Implement a queue using two stacks.

## Trees and Binary Search Trees

**Find the Height of a Binary Tree**: Calculate the height of a binary tree.**Find the Lowest Common Ancestor of Two Nodes in a Binary Tree**: Determine the lowest common ancestor of two nodes.**Validate if a Binary Tree is a Valid Binary Search Tree**: Check if a binary tree follows the properties of a binary search tree.**Serialize and Deserialize a Binary Tree**: Convert a binary tree to a string and vice versa.**Implement an Inorder Traversal of a Binary Tree**: Write a function for inorder traversal.**Find the Diameter of a Binary Tree**: Calculate the longest path between any two nodes in a binary tree.**Convert a Binary Tree to its Mirror Tree**: Create a mirror image of the binary tree.

## Graphs

**Implement Depth-First Search (DFS)**: Write a DFS algorithm to traverse a graph.**Implement Breadth-First Search (BFS)**: Write a BFS algorithm for graph traversal.**Find the Shortest Path Between Two Nodes in an Unweighted Graph**: Determine the shortest path using BFS.**Detect a Cycle in an Undirected Graph Using DFS**: Identify cycles in an undirected graph.**Check if a Graph is Bipartite**: Determine if a graph can be colored using two colors.**Find the Number of Connected Components in an Undirected Graph**: Count the connected components using DFS/BFS.**Find Bridges in a Graph**: Identify edges that, when removed, increase the number of connected components.

## Sorting and Searching

**Implement (Bubble, Insertion, Selection, Merge) Sort**: Write sorting algorithms for different sorting techniques.**Implement Quicksort**: Create a function to sort an array using the quicksort algorithm.**Implement Binary Search**: Develop a binary search function to find an element in a sorted array.**Implement Interpolation Search**: Design an interpolation search algorithm.**Find the Kth Smallest Element in an Array**: Identify the kth smallest element in an unsorted array.**Count the Number of Inversions in an Array**: Determine how many pairs of elements are out of order in the array.

**Authored by:** Rajat Gajbhiye on Linkedin