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 93 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0001Two SumEasy
- 0003Longest Substring Without Repeating CharactersMed
- 0004Median of Two Sorted ArraysHard
- 0005Longest Palindromic SubstringMed
- 0009Palindrome NumberEasy
- 0012Integer to RomanMed
- 0013Roman to IntegerEasy
- 0014Longest Common PrefixEasy
- 0017Letter Combinations of a Phone NumberMed
- 0020Valid ParenthesesEasy
- 0022Generate ParenthesesMed
- 0028Find the Index of the First Occurrence in a StringEasy
- 0031Next PermutationMed
- 0042Trapping Rain WaterHard
- 0048Rotate ImageMed
- 0049Group AnagramsMed
- 0051N-QueensHard
- 0053Maximum SubarrayMed
- 0054Spiral MatrixMed
- 0056Merge IntervalsMed
Showing 20 of 93