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Solutions and visual explanations to LeetCode problems, fully tested using official sample test cases that are not locked behind a paywall.

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Unofficial listing

Grind 75

Visit problem set

• Week 1
  1. Two Sum
  2. Valid Parentheses
  3. Merge Two Sorted Lists
  4. Best Time to Buy and Sell Stock
  5. Valid Palindrome
  6. Invert Binary Tree
  7. Valid Anagram
  8. Binary Search
  9. Flood Fill
  10. Lowest Common Ancestor of a Binary Search Tree
  11. Balanced Binary Tree
  12. Linked List Cycle
  13. Implement Queue using Stacks
• Week 2
  1. First Bad Version
  2. Ransom Note
  3. Climbing Stairs
  4. Longest Palindrome
  5. Reverse Linked List
  6. Majority Element
  7. Add Binary
  8. Diameter of Binary Tree
  9. Middle of the Linked List
  10. Maximum Depth of Binary Tree
  11. Contains Duplicate
  12. Maximum Subarray
• Week 3
  1. Insert Interval
  2. 01 Matrix
  3. K Closest Points to Origin
  4. Longest Substring Without Repeating Characters
  5. Three Sum
  6. Binary Tree Level Order Traversal
  7. Clone Graph
  8. Evaluate Reverse Polish Notation
• Week 4
  1. Course Schedule
  2. Implement Trie (Prefix Tree)
  3. Coin Change
  4. Product of Array Except Self
  5. Min Stack
  6. Validate Binary Search Tree
  7. Number of Islands
  8. Rotting Oranges
• Week 5
  1. Search in Rotated Sorted Array
  2. Combination Sum
  3. Permutations
  4. Merge Intervals
  5. Lowest Common Ancestor of a Binary Tree
  6. Time Based Key-Value Store
  7. Accounts Merge
  8. Sort Colors
• Week 6
  1. Word Break
  2. Partition Equal Subset Sum
  3. String to Integer (atoi)
  4. Spiral Matrix
  5. Subsets
  6. Binary Tree Right Side View
  7. Longest Palindromic Substring
  8. Unique Paths
  9. Construct Binary Tree from Preorder and Inorder Traversal
• Week 7
  1. Container With Most Water
  2. Letter Combinations of a Phone Number
  3. Word Search
  4. Find All Anagrams in a String
  5. Minimum Height Trees
  6. Task Scheduler
  7. LRU Cache
• Week 8
  1. Kth Smallest Element in a BST
  2. Minimum Window Substring
  3. Serialize and Deserialize Binary Tree
  4. Trapping Rain Water
  5. Find Median from Data Stream
  6. Word Ladder
  7. Basic Calculator
  8. Maximum Profit in Job Scheduling
  9. Merge k Sorted Lists
  10. Largest Rectangle in Histogram

Neetcode 150

Visit problem set

• Arrays & Hashing
  1. Contains Duplicate
  2. Valid Anagram
  3. Two Sum
  4. Group Anagrams
  5. Top K Frequent Elements
  6. Encode and Decode Strings
  7. Product of Array Except Self
  8. Valid Sudoku
  9. Longest Consecutive Sequence
• Two Pointers
  1. Valid Palindrome
  2. Two Sum II - Input Array Is Sorted
  3. Three Sum
  4. Container With Most Water
  5. Trapping Rain Water
• Sliding Window
  1. Best Time to Buy and Sell Stock
  2. Longest Substring Without Repeating Characters
  3. Longest Repeating Character Replacement
  4. Permutation in String
  5. Minimum Window Substring
  6. Sliding Window Maximum
• Stack
  1. Valid Parentheses
  2. Min Stack
  3. Evaluate Reverse Polish Notation
  4. Generate Parentheses
  5. Daily Temperatures
  6. Car Fleet
  7. Largest Rectangle in Histogram
• Binary Search
  1. Binary Search
  2. Search in Rotated Sorted Array
  3. Find Minimum in Rotated Sorted Array
  4. Search a 2D Matrix
  5. Search a 2D Matrix II
  6. Kth Smallest Element in a Sorted Matrix
  7. Find Peak Element
  8. Peak Index in a Mountain Array
• Linked List
  1. Reverse Linked List
  2. Merge Two Sorted Lists
  3. Linked List Cycle
  4. Reorder List
  5. Remove Nth Node From End of List
  6. Copy List with Random Pointer
  7. Add Two Numbers
  8. Find The Duplicate Number
  9. LRU Cache
  10. Merge k Sorted Lists
  11. Reverse Nodes in K-Group
• Trees
  1. Invert Binary Tree
  2. Maximum Depth of Binary Tree
  3. Diameter of Binary Tree
  4. Balanced Binary Tree
  5. Same Tree
  6. Subtree of Another Tree
  7. Lowest Common Ancestor of a Binary Search Tree
  8. Binary Tree Level Order Traversal
  9. Binary Tree Right Side View
  10. Count Good Nodes in Binary Tree
  11. Validate Binary Search Tree
  12. Kth Smallest Element in a BST
  13. Construct Binary Tree from Preorder and Inorder Traversal
  14. Binary Tree Maximum Path Sum
  15. Serialize and Deserialize Binary Tree
• Heap / Priority Queue
  1. Kth Largest Element in a Stream
  2. Last Stone Weight
  3. K Closest Points to Origin
  4. Kth Largest Element in an Array
  5. Task Scheduler
  6. Design Twitter
  7. Find Median from Data Stream
• Backtracking
  1. Subsets
  2. Combination Sum
  3. Combination Sum II
  4. Permutations
  5. Subsets II
  6. Word Search
  7. Palindrome Partitioning
  8. Letter Combinations of a Phone Number
  9. N-Queens
• Tries
  1. Implement Trie Prefix Tree
  2. Design Add and Search Words Data Structure
  3. Word Search II
• Graphs
  1. Number of Islands
  2. Max Area of Island
  3. Clone Graph
  4. Walls and Gates
  5. Rotting Oranges
  6. Pacific Atlantic Water Flow
  7. Surrounded Regions
  8. Course Schedule
  9. Course Schedule II
  10. Graph Valid Tree
  11. Number of Connected Components in an Undirected Graph
  12. Redundant Connection
  13. Word Ladder
• Advanced Graphs
  1. Network Delay Time
  2. Reconstruct Itinerary
  3. Min Cost to Connect All Points
  4. Swim in Rising Water
  5. Alien Dictionary
  6. Cheapest Flights Within K Stops
• 1-D Dynamic Programming
  1. Climbing Stairs
  2. Min Cost Climbing Stairs
  3. House Robber
  4. House Robber II
  5. Longest Palindromic Substring
  6. Palindromic Substrings
  7. Decode Ways
  8. Coin Change
  9. Maximum Product Subarray
  10. Word Break
  11. Longest Increasing Subsequence
  12. Partition Equal Subset Sum
• 2-D Dynamic Programming
  1. Unique Paths
  2. Longest Common Subsequence
  3. Best Time to Buy And Sell Stock With Cooldown
  4. Coin Change II
  5. Target Sum
  6. Interleaving String
  7. Longest Increasing Path In a Matrix
  8. Distinct Subsequences
  9. Edit Distance
  10. Burst Balloons
  11. Regular Expression Matching
• Greedy
  1. Maximum Subarray
  2. Jump Game
  3. Jump Game II
  4. Gas Station
  5. Hand of Straights
  6. Merge Triplets to Form Target Triplet
  7. Partition Labels
  8. Valid Parenthesis String
• Intervals
  1. Insert Interval
  2. Merge Intervals
  3. Non Overlapping Intervals
  4. Meeting Rooms
  5. Meeting Rooms II
  6. Minimum Interval to Include Each Query
• Math & Geometry
  1. Rotate Image
  2. Spiral Matrix
  3. Set Matrix Zeroes
  4. Happy Number
  5. Plus One
  6. Pow(x, n)
  7. Multiply Strings
  8. Detect Squares
• Bit Manipulation
  1. Single Number
  2. Number of 1 Bits
  3. Counting Bits
  4. Reverse Bits
  5. Missing Number
  6. Sum of Two Integers
  7. Reverse Integer

Official listing