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 690 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0003Longest Substring Without Repeating CharactersMed
- 0005Longest Palindromic SubstringMed
- 0006Zigzag ConversionMed
- 0008String to Integer (atoi)Med
- 0010Regular Expression MatchingHard
- 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
- 0030Substring with Concatenation of All WordsHard
- 0032Longest Valid ParenthesesHard
- 0038Count and SayMed
- 0043Multiply StringsMed
- 0044Wildcard MatchingHard
- 0049Group AnagramsMed
- 0058Length of Last WordEasy
- 0065Valid NumberHard
Showing 20 of 690