LeetCode problem walkthroughs
The key insight, optimal strategy, and complexity for the problems that come up most — each with a free interactive walkthrough you can step through, no account needed.
51 problems and counting
Koko Eating BananasBinary SearchWalkthrough
Medium
Reverse Linked ListWalkthroughEasy
Merge Two Sorted ListsWalkthroughEasy
Merge k Sorted ListsHeap / Priority QueueHard
Linked List CycleFast & Slow PointersWalkthroughEasy
Find the Duplicate NumberFast & Slow PointersWalkthroughMedium
Invert Binary TreeGraph Traversal (BFS & DFS)WalkthroughEasy
Maximum Depth of Binary TreeGraph Traversal (BFS & DFS)WalkthroughEasy
Binary Tree Level Order TraversalGraph Traversal (BFS & DFS)WalkthroughMedium
Number of IslandsGraph Traversal (BFS & DFS)Union-Find (Disjoint Set)WalkthroughMedium
Clone GraphGraph Traversal (BFS & DFS)WalkthroughMedium
Course ScheduleTopological SortGraph Traversal (BFS & DFS)WalkthroughMedium