README.md

Problems

• Array & String
  • 2D Array/Matrix
  • Intervals
  • Sliding Window
    • Cumulative Sum
    • Subarray
    • Substring
      • Palindrome
      • String Matching
  • String Calculations
  • Subarray
  • Two Pointers
    • kSum
    • Shortest Word Distance
• Binary Search
• Bitwise Manipulation
• Design
• Dynamic Programming
  • Fibonacci
  • Matrix
  • Subsequence
    • Longest Common Subsequence
    • Longest Increasing Subsequence
  • State Transition by Inaction | Dynamic Programming State Machine
    • Best Time to Buy and Sell Stock
  • Maximum Subarray
  • Prefix Sum
• Graph
  • Breadth-First Search in Graph
  • Depth-First Search in Graph
  • Topological Sort
  • Union Find
• Greedy
• Hash Map/Hash Set
  • Hash Map
  • Hash Set
• Heap/Priority Queue
• Linked List
• Recursion
  • Catalan Number
  • Backtracking
• Stack & Queue
  • Breadth-First Search (BFS)
  • Depth-First Search (DFS)
    • Spiral Matrix
  • Queue
    • Monotonic Queue
  • Stack
    • Basic Calculator
    • Monotonic Stack
    • Polish Notation
• Tree
  • Binary Tree
    • Path Sum
  • Binary Search Tree
• Trie

Array & String

• ⛔⛔⛔ 135. Candy
• 🍀 163. Missing Ranges
• 🍀 168. Excel Sheet Column Title Math
• 🍀 169. Majority Element Sort Hash Map Hash Set Bitwise Manipulations Boyer-Moore Voting Algorithm Divide & Conquer Math
• 🍀 228. Summary Ranges
• ⚠️⚠️ 229. Majority Element II Hash Map Boyer-Moore Voting Algorithm
• ⚠️⚠️ 238. Product of Array Except Self Prefix Sum Two Pointers
• 🍀 293. Flip Game
• ⚠️⚠️ 334. Increasing Triplet Subsequence
• ⚠️⚠️ 443. String Compression
• ⛔⛔⛔ 956. Tallest Billboard Dynamic Programming
• 🍀 859. Buddy Strings
• 🍀 896. Monotonic Array
• 🍀 1071. Greatest Common Divisor of Strings
• 🍀 1232. Check If It Is a Straight Line Math
• 🍀 1431. Kids With the Greatest Number of Candies
• 🍀 1464. Maximum Product of Two Elements in an Array Priority Queue Sorting
• 🍀 1491. Average Salary Excluding the Minimum and Maximum Salary
• 🍀 1502. Can Make Arithmetic Progression From Sequence Sorting
• ⚠️⚠️ 1503. Last Moment Before All Ants Fall Out of a Plank Brainteasing
• ⚠️⚠️ 1561. Maximum Number of Coins You Can Get
• ⚠️⚠️ 1630. Arithmetic Subarrays Sort Math
• 🍀 1716. Calculate Money in Leetcode Bank Math
• 🍀 1822. Sign of the Product of an Array
• ⚠️⚠️ 1887. Reduction Operations to Make the Array Elements Equal Sorting
• 🍀 1909. Remove One Element to Make the Array Strictly Increasing
• 🍀 1913. Maximum Product Difference Between Two Pairs Sort Priority Queue
• 🍀 2264. Largest 3-Same-Digit Number in String Hash Map
• ⚠️⚠️ 2483. Minimum Penalty for a Shop
• 🍀 2660. Determine the Winner of a Bowling Game Brainteasing
• 🍀 2706. Buy Two Chocolates Priority Queue Counting Sort Bucket Sort Greedy Algorithm
• ⚠️⚠️ 2966. Divide Array Into Arrays With Max Difference Sorting
• ⚠️⚠️ 2971. Find Polygon With the Largest Perimeter Sorting

2D Array/Matrix

• ⚠️⚠️ 36. Valid Sudoku Array & String Hash Set Bitwise Manipulation
• ⚠️⚠️ 311. Sparse Matrix Multiplication
• ⚠️⚠️ 498. Diagonal Traverse Depth First Search Hash Map
• ⚠️⚠️ 1055. Shortest Way to Form String Two Pointers Binary Search 2D Array Dynamic Programming
• ⛔⛔⛔ 1074. Number of Submatrices That Sum to Target Prefix Sum
• 🍀 1351. Count Negative Numbers in a Sorted Matrix Binary Search Linear Traversal
• ⚠️⚠️ 1428. Leftmost Column with at Least a One Binary Search Vertical Traversal
• 🍀 1582. Special Positions in a Binary Matrix Hash Map Sorting

Intervals

• ⚠️⚠️ 56. Merge Intervals Sorting Graph Union-Find
• ⚠️⚠️ 57. Insert Interval Binary Search
• 🍀 252. Meeting Rooms Sorting
• ⚠️⚠️ 253. Meeting Rooms II Priority Queue Chronological Ordering Sorting
• ⚠️⚠️ 435. Non-overlapping Intervals Greedy
• ⚠️⚠️ 452. Minimum Number of Arrows to Burst Balloons Greedy
• ⚠️⚠️ 624. Maximum Distance in Arrays Greedy
• ⛔⛔⛔ 1235. Maximum Profit in Job Scheduling Dynamic Programming Priority Queue Sorting
• ⚠️⚠️ 1272. Remove Interval Greedy
• ⛔⛔⛔ 2402. Meeting Rooms III Priority Queue Sorting

Sliding Window

• ⚠️⚠️ 438. Find All Anagrams in a String

• ⚠️⚠️ 487. Max Consecutive Ones II

• ⚠️⚠️ 567. Permutation in String Hash Map Two Pointers

• ⚠️⚠️ 904. Fruit Into Baskets Sliding Window Two Pointers Hash Map

• ⚠️⚠️ 1004. Max Consecutive Ones III

• 🍀 1065. Index Pairs of a String Trie Hash Set

• ⚠️⚠️ 1291. Sequential Digits

• ⚠️⚠️ 1493. Longest Subarray of 1's After Deleting One Element Two Pointers

• ⚠️⚠️ 1759. Count Number of Homogenous Substrings

• ⛔⛔⛔ 2009. Minimum Number of Operations to Make Array Continuous Binary Search

• Cumulative Sum

  • 🍀 643. Maximum Average Subarray I Math
  • ⚠️⚠️ 2090. K Radius Subarray Averages

• Subarray

  • ⚠️⚠️ 209. Minimum Size Subarray Sum
  • ⚠️⚠️ 2348. Number of Zero-Filled Subarrays

• Substring

  • ⚠️⚠️ 3. Longest Substring Without Repeating Characters Hash Map

  • ⛔⛔⛔ 76. Minimum Window Substring

  • ⚠️⚠️ 159. Longest Substring with At Most Two Distinct Characters Sliding Window Two Pointers Hash Map

  • ⚠️⚠️ 340. Longest Substring with At Most K Distinct Characters Sliding Window Hash Map Binary Search

  • ⚠️⚠️ 424. Longest Repeating Character Replacement Hash Map Hash Set

  • ⚠️⚠️ 1456. Maximum Number of Vowels in a Substring of Given Length

  • ⚠️⚠️ 2024. Maximize the Confusion of an Exam Hash Map Binary Search

  • Palindrome

    • ⚠️⚠️ 5. Longest Palindromic Substring Dynamic Programming Sliding Window Two Pointers Manacher's Algorithm
    • 🍀 125. Valid Palindrome
    • ⚠️⚠️ 647. Palindromic Substrings Dynamic Programming Manacher's Algorithm
    • ⛔⛔⛔ 1216. Valid Palindrome III Dynamic Programming Breadth-First Search Two Pointers

  • String Matching

    • 🍀 28. Find the Index of the First Occurrence in a String Sliding Window Rabin-Karp Algorithm Knuth–Morris–Pratt Algorithm
    • 🍀 459. Repeated Substring Pattern Rabin-Karp Algorithm Knuth–Morris–Pratt Algorithm
    • ⚠️⚠️ 686. Repeated String Match Rabin-Karp Algorithm Knuth–Morris–Pratt Algorithm

String Calculations

• ⚠️⚠️ 43. Multiply Strings
• [66. Plus One]
• [67. Add Binary]
• 🍀 258. Add Digits Math
• [415. Add Strings]
• [989. Add to Array-Form of Integer]

Two Pointers

696. Count Binary Substrings
697. Subarray Product Less Than K
698. Binary Subarrays With Sum parent problem for 3 pointers -> 992. Subarrays with K Different Integers
699. Number of Substrings Containing All Three Characters
700. Number of Substrings With Only 1s
701. Longest Substring Of All Vowels in Order
702. Count Vowel Substrings of a String
703. Vowels of All Substrings
704. Count Subarrays With Score Less Than K

• ⚠️⚠️ 11. Container With Most Water
• ⚠️⚠️ 151. Reverse Words in a String
• ⚠️⚠️ 189. Rotate Array
• 🍀 283. Move Zeroes
• 🍀 344. Reverse String
• 🍀 345. Reverse Vowels of a String
• 🍀 392. Is Subsequence Greedy Algorithm Divide & Conquer Dynamic Programming
• 🍀 455. Assign Cookies Sorting
• 🍀 557. Reverse Words in a String III
• 🍀 905. Sort Array By Parity
• 🍀 977. Squares of a Sorted Array Heap Sorting
• ⚠️⚠️ 1441. Build an Array With Stack Operations
• ⚠️⚠️ 1498. Number of Subsequences That Satisfy the Given Sum Condition Binary Search
• ⚠️⚠️ 1578. Minimum Time to Make Rope Colorful Greedy
• 🍀 1099. Two Sum Less Than K Sorting Binary Search Counting Sort
• ⚠️⚠️ 1679. Max Number of K-Sum Pairs Hash Map Sorting
• ⚠️⚠️ 1750. Minimum Length of String After Deleting Similar Ends Array & String Two Pointers
• 🍀 1768. Merge Strings Alternately
• ⚠️⚠️ 1877. Minimize Maximum Pair Sum in Array Sorting

kSum

• 🍀 1. Two Sum Hash Table
• ⚠️⚠️ 15. 3Sum
• ⚠️⚠️ 16. 3Sum Closest Binary Search
• ⚠️⚠️ 18. 4Sum
• ⚠️⚠️ 167. Two Sum II - Input Array Is Sorted Hash Table
• ⚠️⚠️ 454. 4Sum II
• 🍀 1099. Two Sum Less Than K

Shortest Word Distance

• ⚠️⚠️ 245. Shortest Word Distance III

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Binary Search

• ⛔⛔⛔ 4. Median of Two Sorted Arrays

• ⚠️⚠️ 33. Search in Rotated Sorted Array

• ⚠️⚠️ 34. Find First and Last Position of Element in Sorted Array

• 🍀 35. Search Insert Position

• 🍀 69. Sqrt(x) Math Bitwise Manipulation

• ⚠️⚠️ 74. Search a 2D Matrix

• ⚠️⚠️ 81. Search in Rotated Sorted Array II

• ⚠️⚠️ 153. Find Minimum in Rotated Sorted Array

• ⛔⛔⛔ 154. Find Minimum in Rotated Sorted Array II

• ⚠️⚠️ 162. Find Peak Element

• 🍀 278. First Bad Version

• ⚠️⚠️ 287. Find the Duplicate Number

• 🍀 367. Valid Perfect Square Math

• 🍀 374. Guess Number Higher or Lower

• ⚠️⚠️ 658. Find K Closest Elements Sliding Window

• ⚠️⚠️ 702. Search in a Sorted Array of Unknown Size Bitwise Manipulation

• 🍀 704. Binary Search

• ⛔⛔⛔ 719. Find K-th Smallest Pair Distance Heap Prefix Sum Sliding Window

• 🍀 744. Find Smallest Letter Greater Than Target

• ⚠️⚠️ 852. Peak Index in a Mountain Array

• ⚠️⚠️ 875. Koko eating bananas

• ⚠️⚠️ 1011. Capacity To Ship Packages Within D Days

• ⚠️⚠️ 1060. Missing Element in Sorted Array Array & String

• ⛔⛔⛔ 1095. Find in Mountain Array

• 🍀 1287. Element Appearing More Than 25% In Sorted Array

• Minimum number of days to make m bouquets

• Magnetic force between two balls

• Split array largest sum

• Divide chocolate (for premium users only)

• Cutting ribbons (for premium users only)

• 🍀 1539. Kth Missing Positive Number

• ⚠️⚠️ 1802. Maximum Value at a Given Index in a Bounded Array Greedy & Binary Search

• ⚠️⚠️ 1870. Minimum Speed to Arrive on Time

• ⛔⛔⛔ 2141. Maximum Running Time of N Computers Prefix Sum Greedy

• ⚠️⚠️ 2187. Minimum Time to Complete Trips

• ⛔⛔⛔ 2251. Number of Flowers in Full Bloom Priority Queue Two Pointer

• ⚠️⚠️ 2300. Successful Pairs of Spells and Potions Two Pointers

• ⚠️⚠️ 2616. Minimize the Maximum Difference of Pairs

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Bitwise Manipulation

• 🍀 136. Single Number
• ⚠️⚠️ 137. Single Number II Sorting Hash Map Mathematics Karnaugh Map
• 🍀 190. Reverse Bits
• 🍀 191. Number of 1 Bits
• ⚠️⚠️ 201. Bitwise AND of Numbers Range Bitwise Manipulation Brian Kernighan's Algorithm
• 🍀 231. Power of Two
• 🍀 268. Missing Number Sorting Hash Map Hash Set Math
• ⚠️⚠️ 319. Bulb Switcher Brainteaser Math
• 🍀 338. Counting Bits Dynamic Programming
• 🍀 342. Power of Four Math
• 🍀 389. Find the Difference Array & String Counter Hash Map Hash Set Sorting
• ⛔⛔⛔ 458. Poor Pigs Quantum Bit
• ⛔⛔⛔ 847. Shortest Path Visiting All Nodes Graph Dynamic Programming Depth-First Search Breadth-First Search
• ⚠️⚠️ 1066. Campus Bikes II Dynamic Programming Greedy Algorithm Backtracking Dijkstra's Algorithm
• ⚠️⚠️ 1239. Maximum Length of a Concatenated String with Unique Characters Depth-First Search Bitmasking Backtracking Recursion
• ⚠️⚠️ 1318. Minimum Flips to Make a OR b Equal to c
• 🍀 1356. Sort Integers by The Number of 1 Bits Sorting Brian Kerninghan's Algorithm
• ⛔⛔⛔ 1611. Minimum One Bit Operations to Make Integers Zero
• 🍀 2864. Maximum Odd Binary Number Array & String Two Pointers Bit Manipulations

---

Design

• ⚠️⚠️ 146. LRU Cache Ordered Dict Hash Map Linked List

• ⚠️⚠️ 155. Min Stack Monotonic Stack

• ⚠️⚠️ 211. Design Add and Search Words Data Structure Trie Hash Map

• 🍀 232. Implement Queue using Stacks

• ⚠️⚠️ 271. Encode and Decode Strings

• ⚠️⚠️ 284. Peeking Iterator

• ⚠️⚠️ 304. Range Sum Query 2D - Immutable Prefix Sum Dynamic Programming

• ⚠️⚠️ 341. Flatten Nested List Iterator Recursion

• ⚠️⚠️ 348. Design Tic-Tac-Toe Matrix

• ⚠️⚠️ 380. Insert Delete GetRandom O(1)

• ⚠️⚠️ 528. Random Pick with Weight Hash Set

• 🍀 703. K^th Largest Element in a Stream Priority Queue

• 🍀 705. Design HashSet Linked List Binary Search Tree

• 🍀 706. Design HashMap Array & String

• ⛔⛔⛔ 716. Max Stack Linked List Priority Queue

• ⚠️⚠️ 901. Online Stock Span Monotonic Stack

• 🍀 933. Number of Recent Calls Queue

• ⚠️⚠️ 1146. Snapshot Array Binary Search Hash Map

• ⚠️⚠️ 1396. Design Underground System Hash Map

• ⚠️⚠️ 1472. Design Browser History Linked List

• ⚠️⚠️ 1538. Guess the Majority in a Hidden Array

• 🍀 1603. Design Parking System Hash Table

• ⚠️⚠️ 1845. Seat Reservation Manager Priority Queue Sorted Set

• ⚠️⚠️ 2336. Smallest Number in Infinite Set Priority Queue

• ⚠️⚠️ 2353. Design a Food Rating System Priority Queue Hash Map SortedSet

• Implement Stack using Queues

• Design Linked List

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Dynamic Programming

• ⚠️⚠️ 50. Pow(x, n) Binary Search
• ⚠️⚠️ 72. Edit Distance
• ⛔⛔⛔ 87. Scramble String
• ⚠️⚠️ 91. Decode Ways
• ⚠️⚠️ 139. Word Break
• ⚠️⚠️ 256. Paint House
• ⛔⛔⛔ 265. Paint House II
• ⚠️⚠️ 276. Paint Fence
• ⚠️⚠️ 279. Perfect Squares Breadth-First Search
• ⚠️⚠️ 322. Coin Change
• ⚠️⚠️ 368. Largest Divisible Subset
• ⚠️⚠️ 376. Wiggle Subsequence Greedy
• ⚠️⚠️ 377. Combination Sum IV
• ⛔⛔⛔ 403. Frog Jump
• ⛔⛔⛔ 410. Split Array Largest Sum Binary Search
• ⚠️⚠️ 416. Partition Equal Subset Sum
• ⚠️⚠️ 486. Predict the Winner Recursion
• ⚠️⚠️ 518. Coin Change II
• ⚠️⚠️ 651. 4 Keys Keyboard Math
• ⚠️⚠️ 688. Knight Probability in Chessboard
• ⚠️⚠️ 712. Minimum ASCII Delete Sum for Two Strings Recursion
• ⚠️⚠️ 837. New 21 Game
• ⚠️⚠️ 935. Knight Dialer Graph
• ⚠️⚠️ 1043. Partition Array for Maximum Sum
• ⛔⛔⛔ 1187. Make Array Strictly Increasing Binary Search
• ⚠️⚠️ 1140. Stone Game II
• ⚠️⚠️ 1155. Number of Dice Rolls With Target Sum
• ⛔⛔⛔ 1199. Minimum Time to Build Blocks Priority Queue
• ⛔⛔⛔ 1220. Count Vowels Permutation
• ⚠️⚠️ 1218. Longest Arithmetic Subsequence of Given Difference
• ⚠️⚠️ 1230. Toss Strange Coins
• ⛔⛔⛔ 1335. Minimum Difficulty of a Job Schedule
• ⛔⛔⛔ 1359. Count All Valid Pickup and Delivery Options Monotonic Stack
• ⛔⛔⛔ 1406. Stone Game III
• ⛔⛔⛔ 1416. Restore The Array
• ⛔⛔⛔ 1444. Number of Ways of Cutting a Pizza
• ⛔⛔⛔ 1531. String Compression II
• ⛔⛔⛔ 1547. Minimum Cost to Cut a Stick
• ⛔⛔⛔ 1575. Count All Possible Routes
• ⛔⛔⛔ 1751. Maximum Number of Events That Can Be Attended II Binary Search Sorting
• ⚠️⚠️ 2140. Solving Questions With Brainpower
• ⛔⛔⛔ 2147. Number of Ways to Divide a Long Corridor Math
• ⚠️⚠️ 2291. Maximum Profit From Trading Stocks
• ⛔⛔⛔ 2328. Number of Increasing Paths in a Grid
• ⛔⛔⛔ 2355. Maximum Number of Books You Can Take
• ⛔⛔⛔ 2361. Minimum Costs Using the Train Line
• ⚠️⚠️ 2369. Check if There is a Valid Partition For The Array
• ⚠️⚠️ 2466. Count Ways To Build Good Strings
• ⛔⛔⛔ 2742. Painting the Walls
• ⚠️⚠️ 2770. Maximum Number of Jumps to Reach the Last Index

Fibonacci

• 🍀 70. Climbing Stairs Recursion Bitwise Manipulations
• ⚠️⚠️ 198. House Robber
• 🍀 509. Fibonacci Number
• ⚠️⚠️ 740. Delete and Earn
• 🍀 746. Min Cost Climbing Stairs
• 🍀 1137. N-th Tribonacci Number

Matrix

• ⚠️⚠️ 62. Unique Paths
• ⚠️⚠️ 63. Unique Paths II
• ⚠️⚠️ 64. Minimum Path Sum
• 🍀 118. Pascal's Triangle
• ⚠️⚠️ 120. Triangle
• ⚠️⚠️ 221. Maximal Square
• ⚠️⚠️ 799. Champagne Tower
• 🍀 867. Transpose Matrix
• ⚠️⚠️ 931. Minimum Falling Path Sum

Subsequence

Longest Common Subsequence

• ⚠️⚠️ 516. Longest Palindromic Subsequence
• ⛔⛔⛔ 727. Minimum Window Subsequence Greedy Sliding Window
• ⚠️⚠️ 1035. Uncrossed Lines
• ⚠️⚠️ 1143. Longest Common Subsequence
• ⛔⛔⛔ 1312. Minimum Insertion Steps to Make a String Palindrome

Longest Increasing Subsequence

• ⚠️⚠️ 300. Longest Increasing Subsequence Binary Search
• ⚠️⚠️ 673. Number of Longest Increasing Subsequence
• ⚠️⚠️ 1027. Longest Arithmetic Subsequence
• ⚠️⚠️ 1048. Longest String Chain
• ⚠️⚠️ 1218. Longest Arithmetic Subsequence of Given Difference
• ⛔⛔⛔ 1964. Find the Longest Valid Obstacle Course at Each Position Binary Search Greedy
• ⛔⛔⛔ 2407. Longest Increasing Subsequence II Segment Tree Numpy

State Transition by Inaction | Dynamic Programming State Machine

• ⛔⛔⛔ 879. Profitable Schemes
• ⚠️⚠️ 983. Minimum Cost For Tickets
• ⛔⛔⛔ 1402. Reducing Dishes Greedy

Best Time to Buy and Sell Stock

• 🍀 121. Best Time to Buy and Sell Stock
• ⚠️⚠️ 122. Best Time to Buy and Sell Stock II Greedy
• ⛔⛔⛔ 123. Best Time to Buy and Sell Stock III
• ⛔⛔⛔ 188. Best Time to Buy and Sell Stock IV
• ⚠️⚠️ 309. Best Time to Buy and Sell Stock with Cooldown
• ⚠️⚠️ 714. Best Time to Buy and Sell Stock with Transaction Fee Greedy

Maximum Subarray

• ⚠️⚠️ 53. Maximum Subarray Kadane's Algorithm Divide & Conquer

• ⚠️⚠️ 152. Maximum Product Subarray Kadane's Algorithm

• ⛔⛔⛔ 2272. Substring With Largest Variance Kadane's Algorithm

• [718. Maximum Length of Repeated Subarray] Similar Problems: 72, 10, 44, 97, 115, 583, 712, 1187, 1143, 1092, 718

Prefix Sum

• ⚠️⚠️ 560. Subarray Sum Equals K Dynamic Programming Prefix Sum Hash Map
• 🍀 724. Find Pivot Index
• 🍀 1732. Find the Highest Altitude
• ⚠️⚠️ 2439. Minimize Maximum of Array Dynamic Programming
• 🍀 2485. Find the Pivot Integer Binary Search

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Graph

• 🍀 997. Find the Town Judge
• ⚠️⚠️ 1236. Web Crawler Breadth-First Search Depth-First Search
• ⚠️⚠️ 1466. Reorder Routes to Make All Paths Lead to the City Zero Breadth-First Search Depth-First Search
• ⚠️⚠️ 1557. Minimum Number of Vertices to Reach All Nodes Hash Map Hash Set
• ⚠️⚠️ 1615. Maximal Network Rank
• ⚠️⚠️ 1631. Path With Minimum Effort Depth-First Search Breadth-First Search Priority Queue Union-Find Binary Search Tree Dijkstra's Algorithm Backtracking

Breadth-First Search in Graph

• ⚠️⚠️ 210. Course Schedule II Topological Sorting Kahn's Algorithm
• ⚠️⚠️ 802. Find Eventual Safe States Topological Sorting Kahn's Algorithm
• ⛔⛔⛔ 815. Bus Routes
• ⛔⛔⛔ 864. Shortest Path to Get All Keys
• ⚠️⚠️ 1245. Tree Diameter Breadth-First Search Depth-First Search
• ⚠️⚠️ 1514. Path with Maximum Probability Bellman-Ford Algorithm Shortest Path Faster Algorithm Dijkstra's Algorithm
• ⚠️⚠️ 1926. Nearest Exit from Entrance in Maze

Depth-First Search in Graph

• ⚠️⚠️ 133. Clone Graph
• ⛔⛔⛔ 332. Reconstruct Itinerary Backtracking Greedy Hierholzer's Algorithm
• ⚠️⚠️ 841. Keys and Rooms
• ⚠️⚠️ 1254. Number of Closed Islands Breadth-First Search Graph Union-Find
• ⚠️⚠️ 1743. Restore the Array From Adjacent Pairs Linked List
• ⛔⛔⛔ 1857. Largest Color Value in a Directed Graph Topological Sorted Order Kahn's Algorithm
• ⛔⛔⛔ 2360. Longest Cycle in a Graph Topological Sorted Order Kahn's Algorithm

Topological Sort

• ⚠️⚠️ 207. Course Schedule Kahn's Algorithm Depth-First Search Breadth-First Search
• ⚠️⚠️ 1136. Parallel Courses Kahn's Algorithm Depth-First Search Breadth-First Search

Union-Find

• ⚠️⚠️ 399. Evaluate Division Depth-First Search
• ⚠️⚠️ 547. Number of Provinces Breadth-First Search Depth-First Search
• ⛔⛔⛔ 839. Similar String Groups Breadth-First Search Depth-First Search
• ⚠️⚠️ 947. Most Stones Removed with Same Row or Column Breadth-First Search Depth-First Search
• ⚠️⚠️ 1319. Number of Operations to Make Network Connected Breadth-First Search Depth-First Search
• ⛔⛔⛔ 1579. Remove Max Number of Edges to Keep Graph Fully Traversable
• ⚠️⚠️ 1584. Min Cost to Connect All Points Kruskal's Algorithm Prim's Algorithm Union-Find Priority Queue
• ⛔⛔⛔ 1697. Checking Existence of Edge Length Limited Paths
• ⛔⛔⛔ 1970. Last Day Where You Can Still Cross Breadth-First Search Depth-First Search
• ⚠️⚠️ 2316. Count Unreachable Pairs of Nodes in an Undirected Graph Breadth-First Search Depth-First Search
• ⚠️⚠️ 2492. Minimum Score of a Path Between Two Cities Breadth-First Search Depth-First Search

---

Greedy

• 🍀 326. Power of Three Math
• 🍀 409. Longest Palindrome Hash Set Hash Map
• 🍀 605. Can Place Flowers
• ⚠️⚠️ 646. Maximum Length of Pair Chain Dynamic Programming
• ⚠️⚠️ 881. Boats to Save People Two Pointers
• ⚠️⚠️ 946. Validate Stack Sequences Stack
• ⚠️⚠️ 948. Bag of Tokens Sorting Two Pointers Queue
• ⛔⛔⛔ 1183. Maximum Number of Ones
• ⛔⛔⛔ 1326. Minimum Number of Taps to Open to Water a Garden Dynamic Programming
• ⚠️⚠️ 1328. Break a Palindrome
• ⚠️⚠️ 2038. Remove Colored Pieces if Both Neighbors are the Same Color Array & String Regular Expression Greedy Sliding Window
• ⚠️⚠️ 2125. Number of Laser Beams in a Ban
• ⚠️⚠️ 2131. Longest Palindrome by Concatenating Two Letter Words
• ⛔⛔⛔ 2366. Minimum Replacements to Sort the Array
• ⚠️⚠️ 2393. Count Strictly Increasing Subarrays Dynamic Programming
• ⚠️⚠️ 2405. Optimal Partition of String Hash Table
• ⛔⛔⛔ 2551. Put Marbles in Bags Sorting

---

Hash Map/Hash Set

• ⚠️⚠️ 791. Custom Sort String Array & String Hash Map

Hash Map

• ⚠️⚠️ 49. Group Anagrams
• ⚠️⚠️ 347. Top K Frequent Elements Priority Queue Sorting Quickselect (Hoare's Selection Algorithm)
• 🍀 350. Intersection of Two Arrays II
• 🍀 387. First Unique Character in a String
• ⚠️⚠️ 451. Sort Characters By Frequency Priority Queue Bucket Sort
• 🍀 760. Find Anagram Mappings
• 🍀 1160. Find Words That Can Be Formed by Characters
• 🍀 1207. Unique Number of Occurrences
• ⚠️⚠️ 1282. Group the People Given the Group Size They Belong To Greedy
• ⚠️⚠️ 1347. Minimum Number of Steps to Make Two Strings Anagram
• 🍀 1422. Maximum Score After Splitting a String
• ⚠️⚠️ 1647. Minimum Deletions to Make Character Frequencies Unique Priority Queue
• ⚠️⚠️ 1657. Determine if Two Strings Are Close Sorting
• ⚠️⚠️ 1814. Count Nice Pairs in an Array Math
• ⚠️⚠️ 2364. Count Number of Bad Pairs Math
• ⚠️⚠️ 2391. Minimum Amount of Time to Collect Garbage Prefix Sum
• ⚠️⚠️ 2610. Convert an Array Into a 2D Array With Conditions
• ⚠️⚠️ 2870. Minimum Number of Operations to Make Array Empty
• 🍀 3005. Count Elements With Maximum Frequency Array & String Hash Map

Hash Set

• ⚠️⚠️ 128. Longest Consecutive Sequence
• 🍀 202. Happy Number
• 🍀 349. Intersection of Two Arrays Binary Search Two Pointers
• 🍀 645. Set Mismatch Array & String Hash Map Bitwise Manipulation Sorting
• 🍀 1119. Remove Vowels from a String Array & String Hash Set
• 🍀 1496. Path Crossing Hash Map
• 🍀 2215. Find the Difference of Two Arrays Array & String

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Heap/Priority Queue

• ⚠️⚠️ 215. Kth Largest Element in an Array Quickselect Counting Sort
• ⛔⛔⛔ 358. Rearrange String k Distance Apart Greedy
• ⚠️⚠️ 373. Find K Pairs with Smallest Sums
• ⛔⛔⛔ 502. IPO Sorting Dynamic Programming
• ⚠️⚠️ 621. Task Scheduler Greedy Hash Map Math Heap
• ⚠️⚠️ 767. Reorganize String Counter
• 🍀 1046. Last Stone Weight
• 🍀 1086. High Five Sorted List Sorting
• ⚠️⚠️ 1167. Minimum Cost to Connect Sticks
• 🍀 1337. The K Weakest Rows in a Matrix Binary Search Array & String Linear Search Sorting Vertical Iteration
• ⚠️⚠️ 1481. Least Number of Unique Integers after K Removals Hash Map Counting Sort Sorting
• ⚠️⚠️ 1642. Furthest Building You Can Reach Priority Queue Binary Search
• ⚠️⚠️ 1921. Eliminate Maximum Number of Monsters Array & String
• ⚠️⚠️ 2462. Total Cost to Hire K Workers
• ⚠️⚠️ 2542. Maximum Subsequence Score Sorting

---

Linked List

• ⚠️⚠️ 2. Add Two Numbers
• ⚠️⚠️ 19. Remove N^th Node From End of List Two Pointers
• 🍀 21. Merge Two Sorted Lists Recursion
• ⛔⛔⛔ 23. Merge k Sorted Lists Stack Priority Queue Divide & Conquer
• ⚠️⚠️ 24. Swap Nodes in Pairs Recursion
• ⚠️⚠️ 61. Rotate List Two Pointers
• ⚠️⚠️ 86. Partition List Two Pointers
• ⚠️⚠️ 92. Reverse Linked List II
• ⚠️⚠️ 138. Copy List with Random Pointer
• 🍀 141. Linked List Cycle
• ⚠️⚠️ 142. Linked List Cycle II Hash Map Floyd's Tortoise and Hare
• 🍀 206. Reverse Linked List Recursion
• ⚠️⚠️ 382. Linked List Random Node Design Algorithm R
• ⚠️⚠️ 445. Add Two Numbers II Stack Two Pointers Math
• ⚠️⚠️ 725. Split Linked List in Parts
• 🍀 876. Middle of the Linked List Two Pointers Floyd's Tortoise and Hare
• ⚠️⚠️ 1721. Swapping Nodes in a Linked List Two Pointers
• ⚠️⚠️ 1836. Remove Duplicates From an Unsorted Linked List Stack Hash Map Two Pointers
• ⚠️⚠️ 2095. Delete the Middle Node of a Linked List Two Pointers Floyd's Tortoise and Hare
• ⚠️⚠️ 2130. Maximum Twin Sum of a Linked List Stack Two Pointers
• 🍀 3062. Winner of the Linked List Game Two Pointers

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Recursion

• ⚠️⚠️ 576. Out of Boundary Paths Dynamic Programming
• ⛔⛔⛔ 1569. Number of Ways to Reorder Array to Get Same BST
• ⚠️⚠️ 1980. Find Unique Binary String

Catalan Number

• ⚠️⚠️ 95. Unique Binary Search Trees II

Backtracking

• ⚠️⚠️ 17. Letter Combinations of a Phone Number Sorted List
• ⛔⛔⛔ [37. Sudoku Solver]
• ⚠️⚠️ 39. Combination Sum
• ⚠️⚠️ 40. Combination Sum II
• ⚠️⚠️ 216. Combination Sum III
• ⚠️⚠️ 46. Permutations Depth-First Search Breadth-First Search
• [47. Permutations II]
• ⚠️⚠️ 77. Combinations
• [78. Subsets]
• [90. Subsets II]
• [93. Restore IP addresses]
• [131. Palindrome Partitioning]
• ⛔⛔⛔ 465. Optimal Account Balancing Dynamic Programming Bitmasking
• ⚠️⚠️ 784. Lettercase Permutation Dynamic Programming Bitmasking
• [1079 Letter Tile Possibilities]
• [1087. Brace Expansion]
• ⛔⛔⛔ 1601. Maximum Number of Achievable Transfer Requests Dynamic Programming Bitmasking
• ⚠️⚠️ 2305. Fair Distribution of Cookies

---

Stack & Queue

Breadth-First Search (BFS)

286. Walls and Gates
287. As Far from Land as Possible
288. Map of Highest Peak

• ⛔⛔⛔ 296. Best Meeting Point Sort Math
• ⚠️⚠️ 505. The Maze II Depth-First Search Dijkstra's Algorithm Priority Queue A* Search Algorithm
• ⚠️⚠️ 542. 01 Matrix Dynamic Programming
• 🍀 661. Image Smoother
• ⚠️⚠️ 934. Shortest Bridge Depth-First Search Manhattan Distance
• ⚠️⚠️ 994. Rotting Oranges
• ⚠️⚠️ 1091. Shortest Path in Binary Matrix
• ⚠️⚠️ 1197. Minimum Knight Moves Depth-First Search Dijkstra's Algorithm
• ⚠️⚠️ 1424. Diagonal Traverse II Hash Map
• 🍀 1572. Matrix Diagonal Sum Depth-First Search Matrix
• ⚠️⚠️ 1660. Correct a Binary Tree Binary Search

Depth-First Search (DFS)

• ⚠️⚠️ 417. Pacific Atlantic Water Flow
• ⚠️⚠️ 490. The Maze Breadth-First Search
• ⚠️⚠️ 695. Max Area of Island Breadth-First Search
• ⚠️⚠️ 1020. Number of Enclaves Breadth-First Search
• ⚠️⚠️ 2101. Detonate the Maximum Bombs Breadth-First Search Graph

Spiral Matrix

• ⚠️⚠️ 54. Spiral Matrix Breadth-First Search Matrix
• ⚠️⚠️ 59. Spiral Matrix II Breadth-First Search Matrix

Queue

• ⚠️⚠️ 649. Dota2 Senate
• ⚠️⚠️ 1535. Find the Winner of an Array Game

Monotonic Queue

• ⛔⛔⛔ 239. Sliding Window Maximum Sliding Window
• ⛔⛔⛔ 1425. Constrained Subsequence Sum Priority Queue Kadane's Algorithm

Stack

• 🍀 20. Valid Parentheses Hash Map
• ⚠️⚠️ 71. Simplify Path Regular Expression
• ⚠️⚠️ 150. Evaluate Reverse Polish Notation
• ⚠️⚠️ 394. Decode String Regular Expression Recursion
• ⚠️⚠️ 735. Asteroid Collision
• ⚠️⚠️ 880. Decoded String at Index Math
• ⚠️⚠️ 2390. Removing Stars From a String

Basic Calculator

• ⛔⛔⛔ 224. Basic Calculator
• ⚠️⚠️ 227. Basic Calculator II
• ⛔⛔⛔ 772. Basic Calculator III

Monotonic Stack

• ⚠️⚠️ 316. Remove Duplicate Letters Greedy
• ⚠️⚠️ 456. 132 Pattern Binary Search
• 🍀 496. Next Greater Element I Queue Hash Map
• ⚠️⚠️ 739. Daily Temperatures
• ⛔⛔⛔ 1063. Number of Valid Subarrays

Polish Notation

• ⚠️⚠️ 439. Ternary Expression Parser

---

Tree

• ⚠️⚠️ 1376. Time Needed to Inform All Employees Depth-First Search Breadth-First Search Path Compression

Binary Tree

• 🍀 100. Same Tree Breadth-First Search Depth-First Search
• 🍀 101. Symmetric Tree
• ⚠️⚠️ 106. Construct Binary Tree from Inorder and Postorder Traversal
• 🍀 111. Minimum Depth of Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 116. Populating Next Right Pointers in Each Node Breadth-First Search Linked List
• ⚠️⚠️ 129. Sum Root to Leaf Numbers Backtracking Morris Algorithm
• ⚠️⚠️ 199. Binary Tree Right Side View Breadth-First Search Depth-First Search
• ⚠️⚠️ 236. Lowest Common Ancestor of a Binary Tree Backtracking Recursion Depth-First Search
• ⚠️⚠️ 250. Count Univalue Subtrees Depth-First Search
• ⚠️⚠️ 513. Find Bottom Left Tree Value Breadth-First Search Depth-First Search
• ⚠️⚠️ 515. Find Largest Value in Each Tree Row Breadth-First Search Depth-First Search
• 🍀 543. Diameter of Binary Tree Depth-First Search
• 🍀 606. Construct String from Binary Tree Depth-First Search Recursion
• 🍀 617. Merge Two Binary Trees Recursion
• ⚠️⚠️ 662. Maximum Width of Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 863. All Nodes Distance K in Binary Tree Breadth-First Search Depth-First Search
• 🍀 872. Leaf-Similar Trees Breadth-First Search Depth-First Search
• ⚠️⚠️ 894. All Possible Full Binary Trees Dynamic Programming
• ⚠️⚠️ 958. Check Completeness of a Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 1026. Maximum Difference Between Node and Ancestor Depth-First Search Recursion
• ⚠️⚠️ 1161. Maximum Level Sum of a Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 1120. Maximum Average Subtree Depth-First Search Recursion
• ⚠️⚠️ 1372. Longest ZigZag Path in a Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 1448. Count Good Nodes in Binary Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 1457. Pseudo-Palindromic Paths in a Binary Tree Backtracking Recursion Depth-First Search Bitmasking
• ⚠️⚠️ 1485. Clone Binary Tree With Random Pointer Breadth-First Search Depth-First Search
• ⚠️⚠️ 1609. Even Odd Tree Breadth-First Search Depth-First Search
• ⚠️⚠️ 1644. Lowest Common Ancestor of a Binary Tree II Backtracking Recursion Depth-First Search
• ⚠️⚠️ 1973. Count Nodes Equal to Sum of Descendants Depth-First Search
• ⚠️⚠️ 2265. Count Nodes Equal to Average of Subtree Depth-First Search
• ⚠️⚠️ 2385. Amount of Time for Binary Tree to Be Infected Graph Breadth-First Search Depth-First Search

Path Sum

• 🍀 112. Path Sum
• ⛔⛔⛔ 124. Binary Tree Maximum Path Sum
• ⚠️⚠️ 437. Path Sum III Prefix Sum
• ⚠️⚠️ 543. Diameter of Binary Tree

Binary Search Tree

• 🍀 108. Convert Sorted Array to Binary Search Tree
• ⚠️⚠️ 109. Convert Sorted List to Binary Search Tree Linked List
• ⚠️⚠️ 173. Binary Search Tree Iterator Design
• ⚠️⚠️ 230. K^th Smallest Element in a BST
• 🍀 270. Closest Binary Search Tree Value
• ⚠️⚠️ 450. Delete Node in a BST
• 🍀 501. Find Mode in Binary Search Tree Depth-First Search Breadth-First Search Hash Map Morris Traversal
• 🍀 530. Minimum Absolute Difference in BST Depth-First Search
• 🍀 700. Search in a Binary Search Tree
• 🍀 938. Range Sum of BST Depth-First Search
• ⚠️⚠️ 1214. Two Sum BSTs Hash Map Hash Set Depth-First Search Two Pointers Morris Traversal

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Trie

• ⚠️⚠️ 79. Word Search Backtracking
• ⚠️⚠️ 208. Implement Trie (Prefix Tree) Design
• ⚠️⚠️ 692. Top K Frequent Words Hash Map Sorting Priority Queue
• ⚠️⚠️ 1268. Search Suggestions System Sorting Binary Search Two Pointers
• ⚠️⚠️ 1804. Implement Trie II (Prefix Tree) Design
• ⚠️⚠️ 2352. Equal Row and Column Pairs Hash Map
• ⚠️⚠️ 2707. Extra Characters in a String Dynamic Programming