Leetcode

personal leetcode solving record

Algorithms

Array

• 1. Two Sum
• 4. Median of Two Sorted Arrays
• 11. Container With Most Water
• 15. 3Sum
• 16. 3Sum Closest
• 18. 4Sum
• 20. Valid Parentheses
• 26. Remove Duplicates from Sorted Array
• 27. Remove Element
• 33. Search in Rotated Sorted Array
• 35. Search Insert Position
• 36. Valid Sudoku
• 39. Combination Sum
• 42. Trapping Rain Water
• 48. Rotate Image
• 49. Group Anagrams
• 53. Maximum Subarray
• 54. Spiral Matrix
• 55. Jump Game
• 56. Merge Intervals
• 57. Insert Interval
• 66. Plus One
• 73. Set Matrix Zeroes
• 74. Search a 2D Matrix
• 79. Word Search
• 84. Largest Rectangle in Histogram
• 88. Merge Sorted Array
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 118. Pascal's Triangle
• 121. Best Time to Buy and Sell Stock
• 122. Best Time to Buy and Sell Stock II
• 128. Longest Consecutive Sequence
• 150. Evaluate Reverse Polish Notation
• 152. Maximum Product Subarray
• 153. Find Minimum in Rotated Sorted Array
• 167. Two Sum II - Input array is sorted
• 169. Majority Element
• 198. House Robber
• 200. Number of Islands
• 212. Word Search II
• 213. House Robber II
• 217. Contains Duplicate
• 238. Product of Array Except Self
• 239. Sliding Window Maximum
• 268. Missing Number
• 283. Move Zeroes
• 287. Find the Duplicate Number
• 300. Longest Increasing Subsequence
• 322. Coin Change
• 347. Top K Frequent Elements
• 377. Combination Sum IV
• 417. Pacific Atlantic Water Flow
• 435. Non-overlapping Intervals
• 448. Find All Numbers Disappeared in an Array
• 475. Heaters
• 561. Array Partition I
• 628. Maximum Product of Three Numbers
• 665. Non-decreasing Array
• 697. Degree of an Array
• 704. Binary Search
• 717. 1-bit and 2-bit Characters
• 718. Maximum Length of Repeated Subarray
• 739. Daily Temperatures
• 747. Largest Number At Least Twice of Others
• 853. Car Fleet
• 875. Koko Eating Bananas
• 918. Maximum Sum Circular Subarray
• 973. K Closest Points to Origin
• 1046. Last Stone Weight
• 1287. Element Appearing More Than 25% In Sorted Array
• 1512. Number of Good Pairs

String

• 3. Longest Substring Without Repeating Characters
• 5. Longest Palindromic Substring
• 6. Zigzag Conversion
• 8. String to Integer(atoi)
• 10. Regular Expression Matching
• 14. Longest Common Prefix
• 13. Roman to Integer
• 17. Letter Combinations of a PhoneNumber
• 22. Generate Parentheses
• 49. Group Anagrams
• 67. Add Binary
• 76. Minimum Window Substring
• 91. Decode Ways
• 125. Valid Palindrome
• 139. Word Break
• 208. Implement Trie (Prefix Tree)
• 211. Design Add and Search Words Data Structure
• 212. Word Search II
• 242. Valid Anagram
• 297. Serialize and Deserialize Binary Tree
• 344. Reverse String
• 415. Add Strings
• 424. Longest Repeating Character Replacement
• 521. Longest Uncommon Subsequence I
• 522. Longest Uncommon Subsequence II
• 557. Reverse Words in a String III
• 567. Permutation in String
• 647. Palindromic Substrings
• 659. Encode and Decode Strings
• 981. Time Based Key-Value Store
• 1143. Longest Common Subsequence

Hash Table

• 1. Two Sum
• 3. Longest Substring Without Repeating Characters
• 36. Valid Sudoku
• 49. Group Anagrams
• 73. Set Matrix Zeroes
• 76. Minimum Window Substring
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 128. Longest Consecutive Sequence
• 133. Clone Graph
• 136. Single Number
• 138. Copy List with Random Pointer
• 139. Word Break
• 141. Linked List Cycle
• 160. Intersection of Two Linked Lists
• 146. LRU Cache
• 169. Majority Element
• 202. Happy Number
• 204. Count Primes
• 208. Implement Trie (Prefix Tree)
• 217. Contains Duplicate
• 242. Valid Anagram
• 268. Missing Number
• 347. Top K Frequent Elements
• 349. Intersection of Two Arrays
• 424. Longest Repeating Character Replacement
• 448. Find All Numbers Disappeared in an Array
• 567. Permutation in String
• 697. Degree of an Array
• 981. Time Based Key-Value Store
• 1512. Number of Good Pairs

Tree

• 94. Binary Tree Inorder Traversal
• 98. Validate Binary Search Tree
• 100. Same Tree
• 101. Symmetric Tree
• 102. Binary Tree Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 110. Balanced Binary Tree
• 124. Binary Tree Maximum Path Sum
• 144. Binary Tree Preorder Traversal
• 145. Binary Tree Postorder Traversal
• 199. Binary Tree Right Side View
• 226. Invert Binary Tree
• 230. Kth Smallest Element in a BST
• 235. Lowest Common Ancestor of a Binary Search Tree
• 297. Serialize and Deserialize Binary Tree
• 572. Subtree of Another Tree
• 543. Diameter of Binary Tree
• 703. Kth Largest Element in a Stream
• 1448. Count Good Nodes in Binary Tree
• 2385. Amount of Time for Binary Tree to Be Infected

Binary Tree

• 74. Search a 2D Matrix
• 94. Binary Tree Inorder Traversal
• 98. Validate Binary Search Tree
• 100. Same Tree
• 102. Binary Tree Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 110. Balanced Binary Tree
• 124. Binary Tree Maximum Path Sum
• 144. Binary Tree Preorder Traversal
• 145. Binary Tree Postorder Traversal
• 230. Kth Smallest Element in a BST
• 235. Lowest Common Ancestor of a Binary Search Tree
• 297. Serialize and Deserialize Binary Tree
• 543. Diameter of Binary Tree
• 572. Subtree of Another Tree
• 704. Binary Search
• 1448. Count Good Nodes in Binary Tree
• 2385. Amount of Time for Binary Tree to Be Infected

Linked List

• 2. Add Two Numbers
• 19. Remove Nth Node From End of List
• 21. Merge Two Sorted Lists
• 23. Merge k Sorted Lists
• 24. Swap Nodes in Pairs
• 25. Reverse Nodes in k-Group
• 86. Partition List
• 92. Reverse Linked List II
• 138. Copy List with Random Pointer
• 141. Linked List Cycle
• 143. Reorder List
• 146. 146. LRU Cache
• 160. Intersection of Two Linked Lists
• 206. Reverse Linked List
• 234. Palindrome Linked List
• 237. Delete Node in a Linked List

Binary Search

• 4. Median of Two Sorted Arrays
• 33. Search in Rotated Sorted Array
• 35. Search Insert Position
• 69. Sqrt(x)
• 153. Find Minimum in Rotated Sorted Array
• 167. Two Sum II - Input array is sorted
• 226. Invert Binary Tree
• 287. Find the Duplicate Number
• 300. Longest Increasing Subsequence
• 349. Intersection of Two Arrays
• 475. Heaters
• 703. Kth Largest Element in a Stream
• 718. Maximum Length of Repeated Subarray
• 875. Koko Eating Bananas
• 981. Time Based Key-Value Store

Binary Search Tree

• 94. Binary Tree Inorder Traversal
• 98. Validate Binary Search Tree
• 230. Kth Smallest Element in a BST
• 703. Kth Largest Element in a Stream

Two Pointers

• 11. Container With Most Water
• 15. 3Sum
• 16. 3Sum Closest
• 18. 4Sum
• 19. Remove Nth Node From End of List
• 26. Remove Duplicates from Sorted Array
• 27. Remove Element
• 42. Trapping Rain Water
• 86. Partition List
• 88. Merge Sorted Array
• 125. Valid Palindrome
• 141. Linked List Cycle
• 143. Reorder List
• 160. Intersection of Two Linked Lists
• 167. Two Sum II - Input array is sorted
• 234. Palindrome Linked List
• 283. Move Zeroes
• 287. Find the Duplicate Number
• 295. Find Median from Data Stream
• 344. Reverse String
• 349. Intersection of Two Arrays
• 567. Permutation in String

Math

• 2. Add Two Numbers
• 7. Reverse Integer
• 9. Palindrome Number
• 13. Roman to Integer
• 29. Divide Two Integers
• 48. Rotate Image
• 62. Unique Paths
• 66. Plus One
• 67. Add Binary
• 69. Sqrt(x)
• 70. Climbing Stairs
• 150. Evaluate Reverse Polish Notation
• 202. Happy Number
• 204. Count Primes
• 268. Missing Number
• 371. Sum of Two Integers
• 372. Super Pow
• 628. Maximum Product of Three Numbers
• 973. K Closest Points to Origin
• 1512. Number of Good Pairs

Recursion

• 2. Add Two Numbers
• 10. Regular Expression Matching
• 17. Letter Combinations of a PhoneNumber
• 21. Merge Two Sorted Lists
• 24. Swap Nodes in Pairs
• 25. Reverse Nodes in k-Group
• 143. Reorder List
• 206. Reverse Linked List
• 234. Palindrome Linked List

Sort

• 16. 3Sum Closest
• 18. 4Sum
• 23. Merge k Sorted Lists
• 49. Group Anagrams
• 56. Merge Intervals
• 88. Merge Sorted Array
• 169. Majority Element
• 217. Contains Duplicate
• 242. Valid Anagram
• 252. Meeting Rooms
• 253. Meeting Rooms II
• 268. Missing Number
• 295. Find Median from Data Stream
• 347. Top K Frequent Elements
• 349. Intersection of Two Arrays
• 435. Non-overlapping Intervals
• 475. Heaters
• 561. Array Partition I
• 628. Maximum Product of Three Numbers
• 747. Largest Number At Least Twice of Others
• 853. Car Fleet
• 973. K Closest Points to Origin

Counting Sort

• 561. Array Partition I

Topologic Sort

• 207. Course Schedule
• 269. Alien Dictionary

Bucket Sort

• 347. Top K Frequent Elements

Backtracking

• 17. Letter Combinations of a PhoneNumber
• 22. Generate Parentheses
• 39. Combination Sum
• 79. Word Search
• 212. Word Search II

Depth-first Search

• 17. Letter Combinations of a PhoneNumber
• 94. Binary Tree Inorder Traversal
• 98. Validate Binary Search Tree
• 100. Same Tree
• 101. Symmetric Tree
• 104. Maximum Depth of Binary Tree
• 110. Balanced Binary Tree
• 124. Binary Tree Maximum Path Sum
• 133. Clone Graph
• 144. Binary Tree Preorder Traversal
• 145. Binary Tree Postorder Traversal
• 178. Graph Valid Tree
• 199. Binary Tree Right Side View
• 200. Number of Islands
• 207. Course Schedule
• 211. Design Add and Search Words Data Structure
• 226. Invert Binary Tree
• 230. Kth Smallest Element in a BST
• 235. Lowest Common Ancestor of a Binary Search Tree
• 297. Serialize and Deserialize Binary Tree
• 323. Number of Connected Components in an Undirected Graph
• 417. Pacific Atlantic Water Flow
• 543. Diameter of Binary Tree
• 572. Subtree of Another Tree
• 1448. Count Good Nodes in Binary Tree
• 2385. Amount of Time for Binary Tree to Be Infected

Breadth-first Search

• 98. Validate Binary Search Tree
• 100. Same Tree
• 101. Symmetric Tree
• 102. Binary Tree Level Order Traversal
• 104. Maximum Depth of Binary Tree
• 133. Clone Graph
• 178. Graph Valid Tree
• 199. Binary Tree Right Side View
• 200. Number of Islands
• 207. Course Schedule
• 226. Invert Binary Tree
• 235. Lowest Common Ancestor of a Binary Search Tree
• 269. Alien Dictionary
• 297. Serialize and Deserialize Binary Tree
• 322. Coin Change
• 323. Number of Connected Components in an Undirected Graph
• 417. Pacific Atlantic Water Flow
• 1448. Count Good Nodes in Binary Tree
• 2385. Amount of Time for Binary Tree to Be Infected

Brainteaser

• 521. Longest Uncommon Subsequence I

Bit Manipulation

• 29. Divide Two Integers
• 136. Single Number
• 190. Reverse Bits
• 191. Number of 1 Bits
• 268. Missing Number
• 287. Find the Duplicate Number
• 338. Counting Bits
• 371. Sum of Two Integers
• 868. Binary Gap

Divide and Conquer

• 4. Median of Two Sorted Arrays
• 23. Merge k Sorted Lists
• 53. Maximum Subarray
• 105. Construct Binary Tree from Preorder and Inorder Traversal
• 169. Majority Element
• 190. Reverse Bits
• 191. Number of 1 Bits
• 347. Top K Frequent Elements
• 372. Super Pow
• 918. Maximum Sum Circular Subarray
• 973. K Closest Points to Origin

Dynamic Programming

• 5. Longest Palindromic Substring
• 10. Regular Expression Matching
• 22. Generate Parentheses
• 42. Trapping Rain Water
• 53. Maximum Subarray
• 55. Jump Game
• 62. Unique Paths
• 70. Climbing Stairs
• 91. Decode Ways
• 121. Best Time to Buy and Sell Stock
• 124. Binary Tree Maximum Path Sum
• 139. Word Break
• 152. Maximum Product Subarray
• 198. House Robber
• 213. House Robber II
• 300. Longest Increasing Subsequence
• 322. Coin Change
• 338. Counting Bits
• 377. Combination Sum IV
• 435. Non-overlapping Intervals
• 647. Palindromic Substrings
• 718. Maximum Length of Repeated Subarray
• 918. Maximum Sum Circular Subarray
• 1155. Number of Dice Rolls With Target Sum
• 1143. Longest Common Subsequence

Greedy

• 11. Container With Most Water
• 55. Jump Game
• 122. Best Time to Buy and Sell Stock II
• 253. Meeting Rooms II
• 435. Non-overlapping Intervals
• 561. Array Partition I

Graph

• 133. Clone Graph
• 178. Graph Valid Tree
• 207. Course Schedule
• 323. Number of Connected Components in an Undirected Graph

Queue

• 239. Sliding Window Maximum
• 918. Maximum Sum Circular Subarray

Monotonic Queue

• 239. Sliding Window Maximum
• 918. Maximum Sum Circular Subarray

Stack

• 15. 3Sum
• 42. Trapping Rain Water
• 84. Largest Rectangle in Histogram
• 143. Reorder List
• 144. Binary Tree Preorder Traversal
• 145. Binary Tree Postorder Traversal
• 150. Evaluate Reverse Polish Notation
• 155. Min Stack
• 234. Palindrome Linked List
• 739. Daily Temperatures
• 853. Car Fleet

Monotonic Stack

• 42. Trapping Rain Water
• 84. Largest Rectangle in Histogram
• 739. Daily Temperatures
• 853. Car Fleet

Heap

• 23. Merge k Sorted Lists
• 239. Sliding Window Maximum
• 253. Meeting Rooms II
• 295. Find Median from Data Stream
• 347. Top K Frequent Elements
• 703. Kth Largest Element in a Stream
• 973. K Closest Points to Origin
• 1046. Last Stone Weight

Memoization

• 70. Climbing Stairs

Counting

• 169. Majority Element
• 347. Top K Frequent Elements

Sliding Window

• 3. Longest Substring Without Repeating Characters
• 76. Minimum Window Substring
• 239. Sliding Window Maximum
• 424. Longest Repeating Character Replacement
• 567. Permutation in String
• 718. Maximum Length of Repeated Subarray

Rolling Hash

• 718. Maximum Length of Repeated Subarray

Hash Function

• 718. Maximum Length of Repeated Subarray

Trie

• 139. Word Break
• 208. Implement Trie (Prefix Tree)
• 211. Design Add and Search Words Data Structure
• 212. Word Search II

Memoization

• 139. Word Break

Combinatorics

• 62. Unique Paths

Union Find

• 128. Longest Consecutive Sequence
• 178. Graph Valid Tree
• 199. Binary Tree Right Side View
• 200. Number of Islands
• 212. Word Search II
• 323. Number of Connected Components in an Undirected Graph

Matrix

• 36. Valid Sudoku
• 48. Rotate Image
• 54. Spiral Matrix
• 73. Set Matrix Zeroes
• 74. Search a 2D Matrix
• 79. Word Search
• 199. Binary Tree Right Side View
• 200. Number of Islands
• 417. Pacific Atlantic Water Flow

Quickselect

• 347. Top K Frequent Elements
• 973. K Closest Points to Origin

String Matching

• 572. Subtree of Another Tree

Hash Function

• 572. Subtree of Another Tree

Design

• 155. Min Stack
• 146. LRU Cache
• 208. Implement Trie (Prefix Tree)
• 211. Design Add and Search Words Data Structure
• 295. Find Median from Data Stream
• 297. Serialize and Deserialize Binary Tree
• 703. Kth Largest Element in a Stream
• 981. Time Based Key-Value Store

Doubly-Linked List

• 146. LRU Cache

Data Stream

• 295. Find Median from Data Stream
• 703. Kth Largest Element in a Stream

Geometry

• 973. K Closest Points to Origin

Database

Where

• 262. Trips and Users
• 569. Median Employee Salary
• 571. Find Median Given Frequency Of Numbers Problem
• 574. Winning Candidate
• 577. Employee Bonus
• 584. Find Customer Referee
• 585. Investments in 2016
• 586. Customer Placing the Largest Number of Orders
• 595. Big Countries
• 607. Sales Person
• 608. Tree Node
• 620. Not Boring Movies

Join

• 175. Combine Two Tables
• 181. Employees Earning More Than Their Managers
• 183. Customers Who Never Order
• 184. Department Highest Salary
• 185. Department Top Three Salaries
• 196. Delete Duplicate Emails
• 197. Rising Temperature
• 534. Game Play Analysis III
• 550. Game Play Analysis IV
• 570. Managers with at Least 5 Direct Reports
• 571. Find Median Given Frequency Of Numbers Problem
• 574. Winning Candidate
• 577. Employee Bonus
• 607. Sales Person

Grouping

• 182. Duplicate Emails
• 184. Department Highest Salary
• 185. Department Top Three Salaries
• 196. Delete Duplicate Emails
• 262. Trips and Users
• 511. Game Play Analysis I
• 512. Game Play Analysis II
• 534. Game Play Analysis III
• 550. Game Play Analysis IV
• 569. Median Employee Salary
• 570. Managers with at Least 5 Direct Reports
• 574. Winning Candidate
• 578. Get Highest Answer Rate Question
• 585. Investments in 2016
• 596. Classes More Than 5 Students

Function

• 176. Second Highest Salary
• 177. Nth Highest Salary
• 180. Consecutive Numbers
• 184. Department Highest Salary
• 196. Delete Duplicate Emails
• 197. Rising Temperature
• 262. Trips and Users
• 511. Game Play Analysis I
• 512. Game Play Analysis II
• 534. Game Play Analysis III
• 550. Game Play Analysis IV
• 571. Find Median Given Frequency Of Numbers Problem
• 578. Get Highest Answer Rate Question

Window Function

• 176. Second Highest Salary
• 177. Nth Highest Salary
• 178. Rank Scores
• 180. Consecutive Numbers
• 184. Department Highest Salary
• 185. Department Top Three Salaries
• 534. Game Play Analysis III
• 569. Median Employee Salary
• 571. Find Median Given Frequency Of Numbers Problem

LAG()

• 180. Consecutive Numbers

RANKING

• 177. Nth Highest Salary
• 184. Department Highest Salary
• 185. Department Top Three Salaries
• 574. Winning Candidate
• 586. Customer Placing the Largest Number of Orders

CASE-WHEN-ELSE

• 626. Exchange Seats