Problem Library
Browse LeetCode problems by category and difficulty, including Blind 75 and NeetCode 250. Sign in to record your practice and build a daily study plan.
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Arrays & Hashing
- Contains Duplicate · Easy
- Valid Anagram · Easy
- Two Sum · Easy
- Group Anagrams · Medium
- Top K Frequent Elements · Medium
- Product of Array Except Self · Medium
- Valid Sudoku · Medium
- Encode and Decode Strings · Medium
- Longest Consecutive Sequence · Medium
- Longest Common Prefix · Easy
- Remove Element · Easy
- Find the Index of the First Occurrence in a String · Easy
- First Missing Positive · Hard
- Length of Last Word · Easy
- Text Justification · Hard
- Sort Colors · Medium
- Pascal's Triangle · Easy
- Best Time to Buy and Sell Stock II · Medium
- Majority Element · Easy
- Largest Number · Medium
- Repeated DNA Sequences · Medium
- Isomorphic Strings · Easy
Two Pointers
- Valid Palindrome · Easy
- Two Sum II - Input Array Is Sorted · Medium
- 3Sum · Medium
- Container With Most Water · Medium
- Trapping Rain Water · Hard
- 4Sum · Medium
- Remove Duplicates from Sorted Array · Easy
- Remove Duplicates from Sorted Array II · Medium
- Merge Sorted Array · Easy
- Rotate Array · Medium
- Move Zeroes · Easy
- Reverse String · Easy
- Valid Palindrome II · Easy
Sliding Window
- Best Time to Buy and Sell Stock · Easy
- Longest Substring Without Repeating Characters · Medium
- Longest Repeating Character Replacement · Medium
- Permutation in String · Medium
- Minimum Window Substring · Hard
- Sliding Window Maximum · Hard
- Minimum Size Subarray Sum · Medium
- Contains Duplicate II · Easy
- Find K Closest Elements · Medium
Stack
- Valid Parentheses · Easy
- Min Stack · Medium
- Evaluate Reverse Polish Notation · Medium
- Generate Parentheses · Medium
- Daily Temperatures · Medium
- Car Fleet · Medium
- Largest Rectangle in Histogram · Hard
- Simplify Path · Medium
- Implement Stack using Queues · Easy
- Decode String · Medium
- Remove K Digits · Medium
- 132 Pattern · Medium
- Baseball Game · Easy
- Asteroid Collision · Medium
Binary Search
- Binary Search · Easy
- Search a 2D Matrix · Medium
- Koko Eating Bananas · Medium
- Find Minimum in Rotated Sorted Array · Medium
- Search in Rotated Sorted Array · Medium
- Time Based Key-Value Store · Medium
- Median of Two Sorted Arrays · Hard
- Find First and Last Position of Element in Sorted Array · Medium
- Search Insert Position · Easy
- Sqrt(x) · Easy
- Search in Rotated Sorted Array II · Medium
- Populating Next Right Pointers in Each Node · Medium
- Find Peak Element · Medium
- Valid Perfect Square · Easy
Linked List
- Reverse Linked List · Easy
- Merge Two Sorted Lists · Easy
- Reorder List · Medium
- Remove Nth Node From End of List · Medium
- Copy List with Random Pointer · Medium
- Add Two Numbers · Medium
- Linked List Cycle · Easy
- Find the Duplicate Number · Medium
- LRU Cache · Medium
- Merge k Sorted Lists · Hard
- Reverse Nodes in k-Group · Hard
- Swap Nodes in Pairs · Medium
- Rotate List · Medium
- Remove Duplicates from Sorted List · Easy
Trees
- Invert Binary Tree · Easy
- Maximum Depth of Binary Tree · Easy
- Diameter of Binary Tree · Easy
- Balanced Binary Tree · Easy
- Same Tree · Easy
- Subtree of Another Tree · Easy
- Lowest Common Ancestor of a Binary Search Tree · Medium
- Binary Tree Level Order Traversal · Medium
- Binary Tree Right Side View · Medium
- Count Good Nodes in Binary Tree · Medium
- Validate Binary Search Tree · Medium
- Kth Smallest Element in a BST · Medium
- Construct Binary Tree from Preorder and Inorder Traversal · Medium
- Binary Tree Maximum Path Sum · Hard
- Serialize and Deserialize Binary Tree · Hard
- Binary Tree Inorder Traversal · Easy
- Unique Binary Search Trees II · Medium
- Unique Binary Search Trees · Medium
- Symmetric Tree · Easy
- Binary Tree Zigzag Level Order Traversal · Medium
- Construct Binary Tree from Inorder and Postorder Traversal · Medium
- Convert Sorted Array to Binary Search Tree · Easy
- Path Sum · Easy
Tries
- Implement Trie (Prefix Tree) · Medium
- Design Add and Search Words Data Structure · Medium
- Word Search II · Hard
- Extra Characters in a String · Medium
Heap / Priority Queue
- Kth Largest Element in a Stream · Easy
- Last Stone Weight · Easy
- K Closest Points to Origin · Medium
- Kth Largest Element in an Array · Medium
- Task Scheduler · Medium
- Design Twitter · Medium
- Find Median from Data Stream · Hard
- IPO · Hard
- Reorganize String · Medium
- Car Pooling · Medium
- Maximum Performance of a Team · Hard
- Longest Happy String · Medium
Backtracking
- Subsets · Medium
- Combination Sum · Medium
- Permutations · Medium
- Subsets II · Medium
- Combination Sum II · Medium
- Word Search · Medium
- Palindrome Partitioning · Medium
- Letter Combinations of a Phone Number · Medium
- N-Queens · Hard
- Permutations II · Medium
- N-Queens II · Hard
- Combinations · Medium
- Restore IP Addresses · Medium
- Matchsticks to Square · Medium
- Partition to K Equal Sum Subsets · Medium
- Maximum Length of a Concatenated String with Unique Characters · Medium
- Splitting a String Into Descending Consecutive Values · Medium
Graphs
- Number of Islands · Medium
- Clone Graph · Medium
- Max Area of Island · Medium
- Pacific Atlantic Water Flow · Medium
- Surrounded Regions · Medium
- Rotting Oranges · Medium
- Walls and Gates · Medium
- Course Schedule · Medium
- Course Schedule II · Medium
- Redundant Connection · Medium
- Number of Connected Components in an Undirected Graph · Medium
- Graph Valid Tree · Medium
- Word Ladder · Hard
- Evaluate Division · Medium
- Island Perimeter · Easy
- Accounts Merge · Medium
- Open the Lock · Medium
- Is Graph Bipartite? · Medium
- Find Eventual Safe States · Medium
- Snakes and Ladders · Medium
- Shortest Bridge · Medium
Advanced Graphs
- Reconstruct Itinerary · Hard
- Min Cost to Connect All Points · Medium
- Network Delay Time · Medium
- Swim in Rising Water · Hard
- Alien Dictionary · Hard
- Cheapest Flights Within K Stops · Medium
- Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree · Hard
- Path with Maximum Probability · Medium
- Remove Max Number of Edges to Keep Graph Fully Traversable · Hard
- Path With Minimum Effort · Medium
1-D Dynamic Programming
- Climbing Stairs · Easy
- Min Cost Climbing Stairs · Easy
- House Robber · Medium
- House Robber II · Medium
- Longest Palindromic Substring · Medium
- Palindromic Substrings · Medium
- Decode Ways · Medium
- Coin Change · Medium
- Maximum Product Subarray · Medium
- Word Break · Medium
- Longest Increasing Subsequence · Medium
- Partition Equal Subset Sum · Medium
- Triangle · Medium
- Perfect Squares · Medium
- Integer Break · Medium
- Combination Sum IV · Medium
- Concatenated Words · Hard
2-D Dynamic Programming
- Unique Paths · Medium
- Longest Common Subsequence · Medium
- Best Time to Buy and Sell Stock with Cooldown · Medium
- Coin Change II · Medium
- Target Sum · Medium
- Interleaving String · Medium
- Longest Increasing Path in a Matrix · Hard
- Distinct Subsequences · Hard
- Edit Distance · Hard
- Burst Balloons · Hard
- Regular Expression Matching · Hard
- Unique Paths II · Medium
- Minimum Path Sum · Medium
- Maximal Square · Medium
- Ones and Zeroes · Medium
- Longest Palindromic Subsequence · Medium
Greedy
- Maximum Subarray · Medium
- Jump Game · Medium
- Jump Game II · Medium
- Gas Station · Medium
- Hand of Straights · Medium
- Merge Triplets to Form Target Triplet · Medium
- Partition Labels · Medium
- Valid Parenthesis String · Medium
- Maximum Length of Pair Chain · Medium
- Dota2 Senate · Medium
- Maximum Sum Circular Subarray · Medium
- Longest Turbulent Subarray · Medium
- Two City Scheduling · Medium
- Candy · Hard
Intervals
- Insert Interval · Medium
- Merge Intervals · Medium
- Non-overlapping Intervals · Medium
- Meeting Rooms · Easy
- Meeting Rooms II · Medium
- Minimum Interval to Include Each Query · Hard
- Data Stream as Disjoint Intervals · Hard
Math & Geometry
- Rotate Image · Medium
- Spiral Matrix · Medium
- Set Matrix Zeroes · Medium
- Happy Number · Easy
- Plus One · Easy
- Pow(x, n) · Medium
- Multiply Strings · Medium
- Detect Squares · Medium
- Zigzag Conversion · Medium
- Palindrome Number · Easy
- Integer to Roman · Medium
- Roman to Integer · Easy
- Spiral Matrix II · Medium
Bit Manipulation
- Single Number · Easy
- Number of 1 Bits · Easy
- Counting Bits · Easy
- Reverse Bits · Easy
- Missing Number · Easy
- Sum of Two Integers · Medium
- Reverse Integer · Medium
- Add Binary · Easy
- Add to Array-Form of Integer · Easy
- Shuffle the Array · Easy