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 22 matching · 2723 totalSort: id ↑
No.ProblemDifficulty
- 0001Two SumEasy
- 0002Add Two NumbersMed
- 0003Longest Substring Without Repeating CharactersMed
- 0004Median of Two Sorted ArraysHard
- 0009Palindrome NumberEasy
- 0014Longest Common PrefixEasy
- 0026Remove Duplicates from Sorted ArrayEasy
- 0034Find First and Last Position of Element in Sorted ArrayMed
- 0042Trapping Rain WaterHard
- 0110Balanced Binary TreeEasy
- 0121Best Time to Buy and Sell StockEasy
- 0125Valid PalindromeEasy
- 0151Reverse Words in a StringMed
- 0179Rotate ArrayMed
- 0230Valid AnagramEasy
- 0270Move ZeroesEasy
- 0309Coin ChangeMed
- 0496Fibonacci NumberEasy
- 0543Subarray Sum Equals KMed
- 1301Longest Happy StringMed
Showing 20 of 22