Problem catalog

All DSA Problems

75 curated coding problems across 16 categories. Every problem opens in a local-first workspace with starter templates and a verified solution in C++, Java, Python, and Go.

Browse all easy →

Browse all medium →

Browse all hard →

Browse by category →

Arrays & Hashing· 11

Two Sumeasy Contains Duplicateeasy Product of Array Except Selfmedium Maximum Subarraymedium Longest Consecutive Sequencemedium Valid Anagrameasy Group Anagramsmedium Set Matrix Zeroesmedium Spiral Matrixmedium Rotate Imagemedium Encode and Decode Stringsmedium

Two Pointers· 3

3Summedium Container With Most Watermedium Valid Palindromeeasy

Sliding Window· 4

Best Time to Buy and Sell Stockeasy Longest Substring Without Repeating Charactersmedium Longest Repeating Character Replacementmedium Minimum Window Substringhard

Stack· 1

Valid Parentheseseasy

Binary Search· 2

Find Minimum in Rotated Sorted Arraymedium Search in Rotated Sorted Arraymedium

Linked List· 5

Merge Two Sorted Listseasy Reverse Linked Listeasy Linked List Cycleeasy Remove Nth Node From End of Listmedium Reorder Listmedium

Trees· 11

Maximum Depth of Binary Treeeasy Same Treeeasy Invert Binary Treeeasy Binary Tree Maximum Path Sumhard Binary Tree Level Order Traversalmedium Serialize and Deserialize Binary Treehard Subtree of Another Treeeasy Construct Binary Tree from Preorder and Inorder Traversalmedium Validate Binary Search Treemedium Kth Smallest Element in a BSTmedium Lowest Common Ancestor of a Binary Search Treemedium

Tries· 3

Implement Trie (Prefix Tree)medium Design Add and Search Words Data Structuremedium Word Search IIhard

Heap / Priority Queue· 3

Top K Frequent Elementsmedium Merge K Sorted Listshard Find Median from Data Streamhard

Backtracking· 1

Word Searchmedium

Graphs· 7

Clone Graphmedium Course Schedulemedium Pacific Atlantic Water Flowmedium Number of Islandsmedium Alien Dictionaryhard Graph Valid Treemedium Number of Connected Components in an Undirected Graphmedium

Dynamic Programming· 13

Maximum Product Subarraymedium Climbing Stairseasy Coin Changemedium Longest Increasing Subsequencemedium Longest Common Subsequencemedium Word Breakmedium Combination Sum IVmedium House Robbermedium House Robber IImedium Decode Waysmedium Unique Pathsmedium Longest Palindromic Substringmedium Palindromic Substringsmedium

Greedy· 1

Jump Gamemedium

Intervals· 5

Insert Intervalmedium Merge Intervalsmedium Non-overlapping Intervalsmedium Meeting Roomseasy Meeting Rooms IImedium

Bit Manipulation· 5

Sum of Two Integersmedium Number of 1 Bitseasy Counting Bitseasy Missing Numbereasy Reverse Bitseasy