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 599 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0001Two SumEasy
- 0003Longest Substring Without Repeating CharactersMed
- 0012Integer to RomanMed
- 0013Roman to IntegerEasy
- 0017Letter Combinations of a Phone NumberMed
- 0030Substring with Concatenation of All WordsHard
- 0036Valid SudokuMed
- 0037Sudoku SolverHard
- 0041First Missing PositiveHard
- 0049Group AnagramsMed
- 0073Set Matrix ZeroesMed
- 0076Minimum Window SubstringHard
- 0105Construct Binary Tree from Preorder and Inorder TraversalMed
- 0106Construct Binary Tree from Inorder and Postorder TraversalMed
- 0126Word Ladder IIHard
- 0127Word LadderHard
- 0128Longest Consecutive SequenceMed
- 0133Clone GraphMed
- 0138Copy List with Random PointerMed
- 0139Word BreakMed
Showing 20 of 599