Top 100 DSA Interview Questions for Coding Interviews

Data Structures and Algorithms (DSA) is the foundation of technical interviews for software engineers. Acing frequently asked problems provides a solid advantage in your coding interviews. This blog presents the Top 50 DSA Interview Questions, classified for organized preparation.

DSA Interview Questions on Array

Arrays are the building blocks of problem-solving in DSA. Here are some must-ask questions:

1. Reverse a string without using extra space.
2. Check if two strings are anagrams.
3. Find the longest palindromic substring.
4. Find the first character that does not repeat in a string.
5. Implement the Rabin-Karp algorithm for searching a pattern.
6. 3 Sum
7. Container With Most Water
8. Factorial of a large number
9. Trapping Rain Water
10. Chocolate Distribution Problem
11. Insert Interval
12. Merge Intervals
13. Non-overlapping Intervals

DSA Interview Questions on String

Strings are frequently used in technical interviews. These problems will strengthen your skills:

1. Reverse a string without using extra space.
2. Check if two strings are anagrams.
3. Find the longest palindromic substring.
4. Find the first character that does not repeat in a string.
5. Longest Substring Without Repeating
6. Longest Repeating Character Replacement
7. Smallest window containing all characters
8. Check for Anagram
9. Print all anagrams together
10. Check Balanced Parentheses
11. Sentence Palindrome
12. Longest Palindromic Substring
13. Palindromic Substrings
14. Longest Common Prefix

DSA Interview Questions on Linked List

Linked lists assist in learning memory handling and pointer management.

1. Reverse a linked list.
2. Find a cycle in a linked list (Floyd’s cycle detection algorithm).
3. Find the middle node of a linked list.
4. Merge two sorted linked lists.
5. Delete duplicates from a sorted linked list.
6. Merge K Sorted Lists
7. Remove Nth Node From End Of List
8. Reorder List
9. Add 1 to a number represented as linked list
10. Middle of a given linked list
11. Delete last occurrence from linked list

Stack & Queue DSA Interview Questions

Stacks and queues are necessary to understand Last-In-First-Out (LIFO) and First-In-First-Out (FIFO) data structures.

1. Implement a stack using two queues.
2. Implement a queue using two stacks.
3. Find the next greater element using a stack.
4. Implement LRU cache using a linked list and hash map.
5. Check for balanced parentheses using a stack.
6. Check mirror in n-ary tree
7. The Celebrity Problem
8. Length of the longest valid substring
9. Print Right View of a Binary Tree
10. Find the first circular tour that visits all

Recursion & Backtracking DSA Interview Questions

Recursion and backtracking are fundamental techniques to solve complex problems in an efficient manner.

1. Generate all subsets of a set.
2. Print all permutations of a string.
3. N-Queens problem solution.
4. Find all valid combinations of parentheses.
5. Rat in a maze problem.

Binary Tree DSA Interview Questions

Binary trees are the building blocks for many complex data structures.

1. Inorder, Preorder, and Postorder traversal of a binary tree.
2. Find the height of a binary tree.
3. Check if two trees are equal.
4. Find the lowest common ancestor (LCA) of two nodes.
5. Serialize and deserialize a binary tree.

Binary Search Tree (BST) DSA Interview Questions

Binary Search Trees (BSTs) are used extensively in search problems.

1. Search for an element in a BST.
2. Construct a BST from a sorted array.
3. Determine whether a tree is a BST.
4. Find the kth smallest element in a BST.
5. Find the inorder successor of a node.

Graph DSA Interview Questions

Graphs are crucial in real-world applications such as networking, social networks, and maps.

1. Implement BFS and DFS for graph traversal.
2. Detect a cycle in a directed graph using DFS.
3. Find the shortest path in an unweighted graph (BFS).
4. Dijkstra’s algorithm for shortest path.
5. Find the number of islands in a grid (Graph traversal problem).
6. Longest Consecutive Sequence
7. Snake and Ladder Problem
8. Bridges in a graph
9. Check whether a given graph is Bipartite or not
10. Find size of the largest region in Boolean Matrix
11. Flood fill Algorithm
12. Strongly Connected Components
13. Topological Sorting

Sorting & Searching DSA Interview Questions

Sorting and searching algorithms are asked most often in interviews.

1. Binary search in a rotated sorted array.
2. Implement Merge Sort algorithm.
3. Implement Quick Sort algorithm.
4. Count inversions in an array (using Merge Sort modification).
5. Find the median of two sorted arrays.

Dynamic Programming (DP) DSA Interview Questions

DP is essential for solving complicated optimization problems in an efficient manner.

1. Solve the 0/1 Knapsack problem.
2. Find the Longest Common Subsequence (LCS).
3. Solve the Coin Change problem (minimum coins required).
4. Find the maximum profit in a stock buy and sell problem.
5. Calculate the Edit Distance between two strings.
6. Count ways to reach the n’th stair
7. Longest Increasing Subsequence
8. Longest Common Subsequence
9. Word Break Problem
10. Dice Throw 
11. Egg Dropping Puzzle
12. Matrix Chain Multiplication
13. Combination Sum
14. Subset Sum Problem
15. Find maximum possible stolen value from houses
16. Count Possible Decodings of a given Digit Sequence
17. Unique paths in a Grid with Obstacles
18. Jump Game
19. Cutting a Rod
20. Maximum Product Cutting
21. Count number of ways to cover a distance

Conclusion

Learning these 50 DSA Interview questions will greatly improve your problem-solving abilities and get you ready for coding interviews at the best tech companies. Practice, knowledge of the underlying algorithms, and efficient solutions are essential to solving these challenges. To practice interview experience, you can visit to gfg or interviewbit.

Begin solving these problems today and take your coding interview preparation to the next level. To know how to master DSA visit here.