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 78 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0001Two SumEasy
- 0003Longest Substring Without Repeating CharactersMed
- 0010Regular Expression MatchingHard
- 0011Container With Most WaterMed
- 0013Roman to IntegerEasy
- 0021Merge Two Sorted ListsEasy
- 0023Merge k Sorted ListsHard
- 0024Swap Nodes in PairsMed
- 0025Reverse Nodes in k-GroupHard
- 0042Trapping Rain WaterHard
- 0051N-QueensHard
- 0052N-Queens IIHard
- 0056Merge IntervalsMed
- 0071Simplify PathMed
- 0076Minimum Window SubstringHard
- 0105Construct Binary Tree from Preorder and Inorder TraversalMed
- 0116Populating Next Right Pointers in Each NodeMed
- 0117Populating Next Right Pointers in Each Node IIMed
- 0121Best Time to Buy and Sell StockEasy
- 0138Copy List with Random PointerMed
Showing 20 of 78