Problem Library

Master these coding challenges to ace your next technical interview. Handpicked problems with personalized spaced repetition.

All tracks Blind 75 NeetCode 150 NeetCode 250 Striver A to Z SDE Sheet

Showing 43 of 43 problems in Striver A to Z.

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All topics Array Backtracking Binary Search Binary Search Tree Binary Tree Breadth-First Search Combinatorics Counting Depth-First Search Divide and Conquer Dynamic Programming Graph Theory Greedy Hash Table Linked List Math Matrix Monotonic Stack

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Array26Dynamic Programming11Depth-First Search9

These are the topics showing up most often in your current queue.

Title	Difficulty	Topics
1. Two Sum	Easy	ArrayHash Table
2. Add Two Numbers	Medium	Linked ListMathRecursion
5. Longest Palindromic Substring	Medium	Two PointersStringDynamic Programming
15. 3Sum	Medium	ArrayTwo PointersSorting
18. 4Sum	Medium	ArrayTwo PointersSorting
19. Remove Nth Node From End of List	Medium	Linked ListTwo Pointers
21. Merge Two Sorted Lists	Easy	Linked ListRecursion
31. Next Permutation	Medium	ArrayTwo Pointers
33. Search in Rotated Sorted Array	Medium	ArrayBinary Search
42. Trapping Rain Water	Hard	ArrayTwo PointersDynamic Programming+2 more
48. Rotate Image	Medium	ArrayMathMatrix
53. Maximum Subarray	Medium	ArrayDivide and ConquerDynamic Programming
54. Spiral Matrix	Medium	ArrayMatrixSimulation
56. Merge Intervals	Medium	ArraySorting
57. Insert Interval	Medium	Array
62. Unique Paths	Medium	MathDynamic ProgrammingCombinatorics
73. Set Matrix Zeroes	Medium	ArrayHash TableMatrix
79. Word Search	Medium	ArrayStringBacktracking+2 more
91. Decode Ways	Medium	StringDynamic Programming
98. Validate Binary Search Tree	Medium	TreeDepth-First SearchBinary Search Tree+1 more
102. Binary Tree Level Order Traversal	Medium	TreeBreadth-First SearchBinary Tree
104. Maximum Depth of Binary Tree	Easy	TreeDepth-First SearchBreadth-First Search+1 more
110. Balanced Binary Tree	Easy	TreeDepth-First SearchBinary Tree
118. Pascal's Triangle	Easy	ArrayDynamic Programming
121. Best Time to Buy and Sell Stock	Easy	ArrayDynamic Programming
122. Best Time to Buy and Sell Stock II	Medium	ArrayDynamic ProgrammingGreedy
127. Word Ladder	Hard	Hash TableStringBreadth-First Search
128. Longest Consecutive Sequence	Medium	ArrayHash TableUnion-Find
133. Clone Graph	Medium	Hash TableDepth-First SearchBreadth-First Search+1 more
141. Linked List Cycle	Easy	Hash TableLinked ListTwo Pointers
152. Maximum Product Subarray	Medium	ArrayDynamic Programming
153. Find Minimum in Rotated Sorted Array	Medium	ArrayBinary Search
167. Two Sum II - Input Array Is Sorted	Medium	ArrayTwo PointersBinary Search
169. Majority Element	Easy	ArrayHash TableDivide and Conquer+2 more
198. House Robber	Medium	ArrayDynamic Programming
199. Binary Tree Right Side View	Medium	TreeDepth-First SearchBreadth-First Search+1 more
200. Number of Islands	Medium	ArrayDepth-First SearchBreadth-First Search+2 more
206. Reverse Linked List	Easy	Linked ListRecursion
207. Course Schedule	Medium	Depth-First SearchBreadth-First SearchGraph Theory+1 more
210. Course Schedule II	Medium	Depth-First SearchBreadth-First SearchGraph Theory+1 more
213. House Robber II	Medium	ArrayDynamic Programming
229. Majority Element II	Medium	ArrayHash TableSorting+1 more
238. Product of Array Except Self	Medium	ArrayPrefix Sum