DSA
Master the patterns
Search the bank, then filter by difficulty, pattern, data structure, or algorithm. Each problem includes approaches, solutions, and walkthroughs.
Active·2,723
Easy·667
Medium·1,394
Hard·662
Patterns
Recognize the move
Filter the bank by pattern — each card links into the problem index.
Problem index
Browse problems
Search by title, then refine with facets. Sorted by problem ID.
Difficulty
Facets
20 of 41 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0010Regular Expression MatchingHard
- 0012Integer to RomanMed
- 0020Valid ParenthesesEasy
- 0023Merge k Sorted ListsHard
- 0042Trapping Rain WaterHard
- 0043Multiply StringsMed
- 0044Wildcard MatchingHard
- 0056Merge IntervalsMed
- 0060Permutation SequenceHard
- 0118Pascal's TriangleEasy
- 0140Word Break IIHard
- 0146LRU CacheMed
- 0149Max Points on a LineHard
- 0188Number of IslandsMed
- 0190Happy NumberEasy
- 0194Reverse Linked ListEasy
- 0196Implement Trie (Prefix Tree)Med
- 0206The Skyline ProblemHard
- 0223Lowest Common Ancestor of a Binary Search TreeMed
- 0328Flatten Nested List IteratorMed
Showing 20 of 41