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 30 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0004Median of Two Sorted ArraysHard
- 0012Integer to RomanMed
- 0017Letter Combinations of a Phone NumberMed
- 0020Valid ParenthesesEasy
- 0021Merge Two Sorted ListsEasy
- 0041First Missing PositiveHard
- 0042Trapping Rain WaterHard
- 0072Edit DistanceMed
- 0075Sort ColorsMed
- 0088Merge Sorted ArrayEasy
- 0090Subsets IIMed
- 0121Best Time to Buy and Sell StockEasy
- 0128Longest Consecutive SequenceMed
- 0146LRU CacheMed
- 0169Majority ElementEasy
- 0190Happy NumberEasy
- 0195Course ScheduleMed
- 0483Next Greater Element IEasy
- 0543Subarray Sum Equals KMed
- 0600Maximum Length of Pair ChainMed
Showing 20 of 30