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 44 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0002Add Two NumbersMed
- 0009Palindrome NumberEasy
- 0013Roman to IntegerEasy
- 0020Valid ParenthesesEasy
- 0021Merge Two Sorted ListsEasy
- 0025Reverse Nodes in k-GroupHard
- 0048Rotate ImageMed
- 0054Spiral MatrixMed
- 0056Merge IntervalsMed
- 0068Text JustificationHard
- 0071Simplify PathMed
- 0079Word SearchMed
- 0084Largest Rectangle in HistogramHard
- 0121Best Time to Buy and Sell StockEasy
- 0122Best Time to Buy and Sell Stock IIMed
- 0146LRU CacheMed
- 0179Rotate ArrayMed
- 0188Number of IslandsMed
- 0200Word Search IIHard
- 0245Binary Tree PathsEasy
Showing 20 of 44