DSA Practice

Top DSA Interview Questions

Data Structures and Algorithms questions curated for FAANG and top-tier engineering interviews.

45Data Structure Qs

45Algorithm Qs

MediumDifficulty

Filter by Data Structure

Filter by Algorithm

Data Structures

45 questions

All questions are medium-difficulty. Click any question to expand the approach, key points, and time/space complexities.

Patterns covered: Arrays · Linked Lists · Trees · Graphs · DP · Greedy · Backtracking · Two Pointers

Top DSA Interview Questions

Find the majority element in an array (appears > n/2 times)

Product of array except self

Maximum subarray sum (Kadane's Algorithm)

3Sum — find all unique triplets that sum to zero

Container with Most Water

Find all duplicates in an array (values in [1, n])

Spiral order traversal of a matrix

Rotate an n×n matrix in-place by 90°

Subarray sum equals K

Longest consecutive sequence

Detect and find the start of a cycle in a linked list

Reorder linked list: L0→L1→…→Ln becomes L0→Ln→L1→Ln-1→…

Remove the Nth node from the end of a linked list

Add two numbers represented as reversed linked lists

Deep copy a linked list with random pointers

Daily temperatures — next warmer day

Largest rectangle in histogram

Implement a Min Stack with O(1) getMin()

Evaluate Reverse Polish Notation (RPN)

Sliding window maximum using a deque

Binary tree level-order traversal (BFS)

Validate a Binary Search Tree

Lowest Common Ancestor (LCA) of a binary tree

Binary Tree right side view

Diameter of a binary tree

Implement a Trie (Prefix Tree)

Word Search in a 2D grid

Kth largest element in a stream

Find K closest points to the origin

Task scheduler — minimum CPU intervals with cooldown

Number of islands (connected components in grid)

Course schedule — detect cycle in directed graph

Clone a graph

Rotting oranges — minimum time for all to rot (BFS)

Walls and gates — fill distance to nearest gate

Group anagrams together

Top K frequent elements

Longest substring without repeating characters

Design an LRU Cache

Longest palindromic substring

Encode and decode strings (no delimiter in charset)

Minimum window substring containing all chars of T

Find all anagrams of P in S

Sum of two integers without + or - operators

Number of 1 bits (Hamming weight)