THE PROBLEM LIBRARY
Find your next breakthrough.
51 interactive problems across five levels. Every pointer, every decision, every step.
51 problemsLEARN · VISUALIZE · PRACTICE
01
Longest Substring Without Repeating Charactersstrings · sliding window
Medium Visualize02Two Sumarrays · hashmap
Easy Visualize03Binary Searcharrays · binary search
Easy Visualize04Valid Parenthesesstrings · stack
Easy Visualize05Reverse Linked Listlinked list
Easy Visualize06Maximum Depth of Binary Treetrees · recursion
Easy Visualize07Number of Islandsgraphs · dfs
Medium Visualize08Coin Changedynamic programming
Medium Visualize09Valid Palindrometwo pointers · strings
Easy Visualize10Move Zeroesarrays · two pointers
Easy Visualize11Range Sum Queriesprefix sum · arrays
Easy Visualize12Daily Temperaturesstack · arrays
Medium Visualize13Generate Parenthesesbacktracking · recursion
Medium Visualize14Subsetsbacktracking · recursion
Medium Visualize15Binary Tree Inorder Traversaltrees · stack
Easy Visualize16Validate Binary Search Treebinary search tree · trees
Medium Visualize17Kth Largest Elementheap priority queue · arrays
Medium Visualize18Find if Path Existsdfs · graphs
Easy Visualize19Course Scheduletopological sort · graphs
Medium Visualize20Shortest Path in a Gridbfs · shortest path
Medium Visualize21Climbing Stairsdynamic programming
Easy Visualize22House Robberdynamic programming · arrays
Medium Visualize23Merge Intervalsintervals · sorting
Medium Visualize24Single Numberbit manipulation · arrays
Easy Visualize25Contains Duplicatehashset · arrays
Easy Visualize26Valid Anagramhashmap · strings
Easy Visualize27Container With Most Watertwo pointers · arrays
Medium Visualize28Maximum Sum of Size Ksliding window · arrays
Easy Visualize29Find Pivot Indexprefix sum · arrays
Easy Visualize30Search Insert Positionbinary search · arrays
Easy Visualize31Next Greater Elementstack · arrays
Medium Visualize32Permutationsbacktracking · arrays
Medium Visualize33Counting Bitsbit manipulation · arrays
Easy Visualize34Jump Gamegreedy · arrays
Medium Visualize35Longest Increasing Subsequencedynamic programming · arrays
Medium Visualize36Insertion Sortsorting · arrays
Easy Visualize37Squares of a Sorted Arraytwo pointers · arrays
Easy Visualize38Minimum Size Subarray Sumsliding window · arrays
Medium Visualize39Subarray Sum Equals Kprefix sum · hashmap
Medium Visualize40Longest Consecutive Sequencehashset · arrays
Medium Visualize41Search in Rotated Sorted Arraybinary search · arrays
Medium Visualize42Simplify Unix Pathstack · strings
Medium Visualize43Combination Sumbacktracking · arrays
Medium Visualize44Unique Grid Pathsdynamic programming · arrays
Medium Visualize45Non-overlapping Intervalsintervals · greedy
Medium Visualize46Happy Numberfast slow pointers
Easy Visualize47Count Connected Componentsunion find · graphs
Medium Visualize48Prefix Word Countstrie · strings
Medium Visualize49Network Delay Timedijkstra · graphs
Medium Visualize50Sliding Window Maximumdeque · arrays
Medium Visualize51Unweighted Graph Distancesbfs · graphs
Medium Visualize