Problem Library

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

Showing 1-20 of 20 matching problems in NeetCode 250.

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Array141Dynamic Programming55String53

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Title	Difficulty	Topics
146. LRU Cache Open source	Medium	Hash TableLinked ListDesign+1 more
155. Min Stack Open source	Medium	StackDesign
208. Implement Trie (Prefix Tree)Open source	Medium	Hash TableStringDesign+1 more
211. Design Add and Search Words Data Structure Open source	Medium	StringDepth-First SearchDesign+1 more
225. Implement Stack using Queues Open source	Easy	StackDesignQueue
232. Implement Queue using Stacks Open source	Easy	StackDesignQueue
271. Encode and Decode Strings Open sourcePremium	Medium	ArrayStringDesign
295. Find Median from Data Stream Open source	Hard	Two PointersDesignSorting+2 more
297. Serialize and Deserialize Binary Tree Open source	Hard	StringTreeDepth-First Search+3 more
304. Range Sum Query 2D - Immutable Open source	Medium	ArrayDesignMatrix+1 more
355. Design Twitter Open source	Medium	Hash TableLinked ListDesign+1 more
460. LFU Cache Open source	Hard	Hash TableLinked ListDesign+1 more
622. Design Circular Queue Open source	Medium	ArrayLinked ListDesign+1 more
703. Kth Largest Element in a Stream Open source	Easy	TreeDesignBinary Search Tree+3 more
705. Design HashSet Open source	Easy	ArrayHash TableLinked List+2 more
706. Design HashMap Open source	Easy	ArrayHash TableLinked List+2 more
895. Maximum Frequency Stack Open source	Hard	Hash TableStackDesign+1 more
901. Online Stock Span Open source	Medium	StackDesignMonotonic Stack+1 more
981. Time Based Key-Value Store Open source	Medium	Hash TableStringBinary Search+1 more
2013. Detect Squares Open source	Medium	ArrayHash TableDesign+2 more