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 25 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0001Two SumEasy
- 0002Add Two NumbersMed
- 0003Longest Substring Without Repeating CharactersMed
- 0007Reverse IntegerMed
- 0009Palindrome NumberEasy
- 0011Container With Most WaterMed
- 0020Valid ParenthesesEasy
- 0021Merge Two Sorted ListsEasy
- 0042Trapping Rain WaterHard
- 0048Rotate ImageMed
- 0053Maximum SubarrayMed
- 0070Climbing StairsEasy
- 0088Merge Sorted ArrayEasy
- 0121Best Time to Buy and Sell StockEasy
- 0122Best Time to Buy and Sell Stock IIMed
- 0125Valid PalindromeEasy
- 0138Copy List with Random PointerMed
- 0141Linked List CycleEasy
- 0146LRU CacheMed
- 0151Reverse Words in a StringMed
Showing 20 of 25