OJ
  • Introduction
  • Some Tips
  • strStr and Coding Style
  • Binary Search
    • 1283. Find the Smallest Divisor Given a Threshold
    • 1898. Maximum Number of Removable Characters
    • 162. Find Peak Element
    • 540. Single Element in a Sorted Array
    • First Position of Target
    • 34. Find First and Last Position of Element in Sorted Array
    • Guess Number Higher or Lower
    • First Bad Version
    • Search Insert Position
    • Search in a Big Sorted Array
    • Convert Binary Search Tree to Sorted Doubly Linked List
    • Search a 2D Matrix
    • 981. Time Based Key-Value Store
    • 362. Design Hit Counter
    • 1348. Tweet Counts Per Frequency
    • 153. Find Minimum in Rotated Sorted Array
    • 33. Search in Rotated Sorted Array
    • Search in Rotated Sorted Array II
    • Heaters
    • Find Right Interval
    • 1060. Missing Element in Sorted Array
    • Is Subsequence
    • Search a 2D Matrix II
    • Find K Closest Elements
    • H-Index II
    • Minimum Size Subarray Sum
    • Median of Two Sorted Arrays
    • 302. Smallest Rectangle Enclosing Black Pixels
    • Longest Increasing Subsequence
      • Russian Doll Envelopes
      • 334. Increasing Triplet Subsequence
    • 二分Range
      • Sqrt
      • Wood Cut
      • Kth Smallest Element in a Sorted Matrix
      • 719. Find K-th Smallest Pair Distance
      • Capacity To Ship Packages Within D Days
      • 668. Kth Smallest Number in Multiplication Table
      • 774. Minimize Max Distance to Gas Station
      • 1631. Path With Minimum Effort
      • 1201. Ugly Number III
    • Find the Unique Number
  • Binary Tree & Divide Conquer
    • Binary Search Tree
      • 1008. Construct Binary Search Tree from Preorder Traversal
      • 449. Serialize and Deserialize BST
      • 109. Convert Sorted List to Binary Search Tree
      • Trim a Binary Search Tree
      • Two Sum IV - Input is a BST
      • Convert BST to Greater Tree
      • 270. Closest Binary Search Tree Value
      • Find Mode in Binary Search Tree
      • Kth Smallest Element in a BST
      • Delete Node in a BST
      • 98. Validate Binary Search Tree
      • Unique Binary Search Trees II
      • 285. Inorder Successor in BST
      • Count of Smaller Numbers After Self
      • 99. Recover Binary Search Tree
      • 235. Lowest Common Ancestor of a Binary Search Tree
      • 295. Find Median from Data Stream
      • 938. Range Sum of BST
      • 1146. Snapshot Array
      • 480. Sliding Window Median
    • Divide & Concquer
      • 226. Invert Binary Tree
      • Insufficient Nodes in Root to Leaf Paths
      • Convert Sorted Array to Binary Search Tree
      • Maximum Depth of Binary Tree
      • 1430. Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree
      • Balanced Binary Tree
      • Binary Tree Tilt
      • 617. Merge Two Binary Trees
      • 100. Same Tree
      • 543. Diameter of Binary Tree
        • Largest BST Subtree
        • Longest Univalue Path
        • 549. Binary Tree Longest Consecutive Sequence II
        • 124. Binary Tree Maximum Path Sum
      • 865. Smallest Subtree with all the Deepest Nodes
      • Second Minimum Node In a Binary Tree
      • Path Sum
        • Path Sum IV
        • Sum Root to Leaf Numbers
        • 437. Path Sum III
      • 236. Lowest Common Ancestor of a Binary Tree
      • 111. Minimum Depth of Binary Tree
      • Maximum Binary Tree
      • Most Frequent Subtree Sum
      • 114. Flatten Binary Tree to Linked List
      • 834. Sum of Distances in Tree
      • 1443. Minimum Time to Collect All Apples in a Tree
      • Construct Binary Tree from Preorder and Inorder Traversal
      • Construct Binary Tree from Inorder and Postorder Traversal
      • Count Complete Tree Nodes
      • Populating Next Right Pointers in Each Node
      • Binary Tree Longest Consecutive Sequence
      • Sum of Left Leaves
      • 87. Scramble String
      • LCA of the Deepest Nodes
      • 统计Distance和覆盖
        • Sum of Distances in Tree
    • Path-recorder Depth-first Search
      • Binary Tree Paths
      • 863. All Nodes Distance K in Binary Tree
      • 606. Construct String from Binary Tree
      • 1367. Linked List in Binary Tree
      • 1343. Maximum Product of Splitted Binary Tree
      • 1457. Pseudo-Palindromic Paths in a Binary Tree
    • Order Traversal
      • Serialize and Deserialize Binary Tree
      • 958. Check Completeness of a Binary Tree
      • 742. Closest Leaf in a Binary Tree
      • Find Duplicate Subtrees
    • 919. Complete Binary Tree Inserter
    • 1519. Number of Nodes in the Sub-Tree With the Same Label
    • 307. Range Sum Query - Mutable
    • 428. Serialize and Deserialize N-ary Tree
    • 315. Count of Smaller Numbers After Self
      • 308. Range Sum Query 2D - Mutable
      • 493. Reverse Pairs
  • Dynamic Programming I
    • 走格
      • 119. Pascal's Triangle II
      • Unique Paths
      • Unique Paths II
      • Climbing Stairs
      • 64. Minimum Path Sum
      • 741. Cherry Pickup
      • Knight Probability in Chessboard
      • Triangle
      • 221. Maximal Square
      • Bomb Enemy
      • 935. Knight Dialer
      • 174. Dungeon Game
      • 818. Race Car
      • 329. Longest Increasing Path in a Matrix
      • 403. Frog Jump
      • 568. Maximum Vacation Days
      • 1344. Jump Game V
    • Subsequence
      • Longest Increasing Subsequence
      • 1395. Count Number of Teams
      • 1027. Longest Arithmetic Sequence
      • Number of Longest Increasing Subsequence
      • Wiggle Subsequence
      • Largest Divisible Subset
      • Maximum Length of Pair Chain
      • 940. Distinct Subsequences II
      • 727. Minimum Window Subsequence
      • Burst Balloons
      • 1458. Max Dot Product of Two Subsequences
      • 1696. Jump Game VI
      • 1626. Best Team With No Conflicts
    • Counting Bits
    • 887. Super Egg Drop
    • 674. Longest Continuous Increasing Subsequence
    • Integer Break
    • Catalan Number
      • Unique Binary Search Trees
      • 22. Generate Parentheses
      • All Possible Full Binary Trees
    • Count Numbers with Unique Digits
    • 2 Keys Keyboard
    • 背包问题
      • Partition Equal Subset Sum
      • 494. Target Sum
      • Ones and Zeroes
      • Perfect Squares
      • Coin Change
      • Combination Sum IV
      • pre背包
        • House Robber
        • House Robber II
      • Coin Change 2
      • 630. Course Schedule III
      • 920. Number of Music Playlists
      • 1235. Maximum Profit in Job Scheduling
      • 1262. Greatest Sum Divisible by Three
    • DFS + Memorization
      • 1444. Number of Ways of Cutting a Pizza
    • Palindromic Strings
      • Palindromic Substrings
      • 5. Longest Palindromic Substring
      • Longest Palindromic Subsequence
      • 1312. Minimum Insertion Steps to Make a String Palindrome
      • 1216. Valid Palindrome III
      • Palindrome Partitioning II
    • 多状态DP
      • Best Time to Buy and Sell Stock
      • Best Time to Buy and Sell Stock with Cooldown
      • Maximum Product Subarray
      • Paint Fence
      • Best Time to Buy and Sell Stock with Transaction Fee
      • Best Time to Buy and Sell Stock IV
      • 975. Odd Even Jump
      • 801. Minimum Swaps To Make Sequences Increasing
      • 552. Student Attendance Record II
    • f长度与input array长度无关
      • Unique Substrings in Wraparound String
    • 多指针
      • Ugly Number II
      • Super Ugly Number
    • Partition
      • 410. Split Array Largest Sum
      • 664. Strange Printer
      • 1335. Minimum Difficulty of a Job Schedule
      • 471. Encode String with Shortest Length
      • 1473. Paint House III
    • Subarray Sum
      • 304. Range Sum Query 2D - Immutable
      • Range Sum Query - Immutable
      • 689. Maximum Sum of 3 Non-Overlapping Subarrays
      • 53. Maximum Subarray
      • Bitwise ORs of Subarrays
      • 363. Max Sum of Rectangle No Larger Than K
      • 901. Online Stock Span
        • 907. Sum of Subarray Minimums
        • 2104. Sum of Subarray Ranges
    • String Match
      • Regular Expression Matching
      • 32. Longest Valid Parentheses
      • 161. One Edit Distance
      • Word Break
      • Decode Ways
        • 639. Decode Ways II
      • KMP
        • 214. Shortest Palindrome
      • Wildcard Matching
      • 97. Interleaving String
      • 1392. Longest Happy Prefix
    • Game Theory
      • Flip Game II
      • Predict the Winner
      • 843. Guess the Word
    • Flip String to Monotone Increasing
    • 1334. Find the City With the Smallest Number of Neighbors at a Threshold Distance
    • Maximum Rectangle
    • 1513. Number of Substrings With Only 1s
    • 哈密顿图
      • 1349. Maximum Students Taking Exam
      • 943. Find the Shortest Superstring
  • Dynamic Programming II
    • 72. Edit Distance
    • Distinct Subsequences
    • Longest Common Substring
    • Longest Common Subsequence
    • Interleaving String
    • House Robber III
  • Linked List
    • 203. Remove Linked List Elements
    • Delete Node in a Linked List
    • Partition List
    • Copy List with Random Pointer
    • Merge k Sorted Lists
    • 148. Sort List
    • Delete Node in a Linked List
    • Merge Two Sorted Lists
    • Add Two Numbers II
    • Swap Nodes in Pairs
    • 2 Pointers with One First Moved N Steps
      • 160. Intersection of Two Linked Lists
      • Remove Nth Node From End of List
      • Rotate List
    • Selection Sort List
    • Insertion Sort List
    • 708. Insert into a Cyclic Sorted List
    • 430. Flatten a Multilevel Doubly Linked List
    • Reverse List
      • 25. Reverse Nodes in k-Group
      • Reverse Linked List
      • Reverse Linked List II
      • Palindrome Linked List
      • Reorder List
    • Remove Nodes
      • Remove Duplicates from Sorted List
      • Remove Duplicates from Sorted List II
    • 876. Middle of the Linked List
    • Linked List Cycle
    • Split Linked List in Parts
  • Array & Numbers
    • 1472. Design Browser History
    • 1291. Sequential Digits
    • 419. Battleships in a Board
    • 48. Rotate Image
    • Perform String Shifts
    • 41. First Missing Positive
    • 73. Set Matrix Zeroes
    • 88. Merge Sorted Array
    • 1347. Minimum Number of Steps to Make Two Strings Anagram
    • Partition Array
    • Median of two Sorted Arrays
    • Reverse Vowels of a String
    • 825. Friends Of Appropriate Ages
    • K-diff Pairs in an Array
    • Longest Word in Dictionary through Deleting
    • Presum
      • Subarray Sum
      • 1352. Product of the Last K Numbers
      • 238. Product of Array Except Self
      • Maximum Subarray II
      • 523. Continuous Subarray Sum
      • Subarray Sum Closest
      • Find Pivot Index
      • 918. Maximum Sum Circular Subarray
      • 930. Binary Subarrays With Sum
      • 974. Subarray Sums Divisible by K
    • Spiral Matrix
      • Spiral Matrix II
      • Spiral Matrix III
      • 498. Diagonal Traverse
      • 766. Toeplitz Matrix
    • Intervals
      • 56. Merge Intervals
      • 352. Data Stream as Disjoint Intervals
      • Merge Two Interval Lists
      • Insert Interval
      • Meeting Rooms
      • 1094. Car Pooling
      • 986. Interval List Intersections
      • 715. Range Module
    • 状态机
      • Game of Life
    • Find All Numbers Disappeared in an Array
    • 406. Queue Reconstruction by Height
    • Flip String to Monotone Increasing
    • Find the Celebrity
    • 扫描线
      • The Skyline Problem
      • 253. Meeting Rooms II
        • 850. Rectangle Area II
        • 732. My Calendar III
      • 759. Employee Free Time
      • 1674. Minimum Moves to Make Array Complementary
    • 463. Island Perimeter
    • 665. Non-decreasing Array
    • 逆推手牌
    • 1354. Construct Target Array With Multiple Sums
    • 780. Reaching Points
    • Rotate Array
    • 969. Pancake Sorting
    • 151. Reverse Words in a String
    • Partition
      • K Empty Slots
    • Sorting
      • 910. Smallest Range II
      • Two City Scheduling
      • 791. Custom Sort String
      • 164. Maximum Gap
      • 1005. Maximize Sum Of Array After K Negations
    • 1006. Clumsy Factorial
    • 1007. Minimum Domino Rotations For Equal Row
    • 896. Monotonic Array
    • 1333. Filter Restaurants by Vegan-Friendly, Price and Distance
    • 1351. Count Negative Numbers in a Sorted Matrix
      • Leftmost Column with at Least a One
    • 1366. Rank Teams by Votes
    • 1332. Remove Palindromic Subsequences
    • 1375. Bulb Switcher III
    • 1389. Create Target Array in the Given Order
    • 1465. Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts
    • 448. Find All Numbers Disappeared in an Array
    • 1422. Maximum Score After Splitting a String
    • 280. Wiggle Sort
  • Heap
    • Merge k Sorted Arrays
    • Heapify
    • 1046. Last Stone Weight
    • Merge k Sorted Lists
    • Ugly Number
    • 373. Find K Pairs with Smallest Sums
    • 1439. Find the Kth Smallest Sum of a Matrix With Sorted Rows
    • 857. Minimum Cost to Hire K Workers
    • 选出出现频率最高的K个
      • Top K Frequent Words
      • Sort Characters By Frequency
      • 347. Top K Frequent Elements
    • Design Twitter
    • Median of K Sorted Array
    • 239. Sliding Window Maximum
    • 1438. Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit
    • 1705. Maximum Number of Eaten Apples
    • 1425. Constrained Subsequence Sum
  • Hash
    • Rehashing
    • Longest Consecutive Sequence
    • Distribute Candies
    • Valid Anagram
    • 统计频率
      • Longest Palindrome
      • Number of Boomerangs
      • Longest Harmonious Subsequence
      • Brick Wall
      • 266. Palindrome Permutation
      • Pairs of Songs With Total Durations Divisible by 60
      • 1394. Find Lucky Integer in an Array
      • 1497. Check If Array Pairs Are Divisible by k
    • Overlapping
      • Minimum Index Sum of Two Lists
      • Keyboard Row
      • Implement Magic Dictionary
      • Valid Sudoku
      • 1452. People Whose List of Favorite Companies Is Not a Subset of Another List
    • 见过
      • Isomorphic Strings
      • 1346. Check If N and Its Double Exist
      • Two Sum
      • 1396. Design Underground System
      • Word Pattern
      • 957. Prison Cells After N Days
      • 939. Minimum Area Rectangle
      • Contains Duplicate II
      • 49. Group Anagrams
      • Counting Elements
      • 249. Group Shifted Strings
      • Bulls and Cows
      • 146. LRU Cache
      • 460. LFU Cache
      • First Unique Number
      • 432. All O`one Data Structure
      • 336. Palindrome Pairs
      • 1282. Group the People Given the Group Size They Belong To
      • 166. Fraction to Recurring Decimal
      • Unique Word Abbreviation
      • Task Schedule with Original Order
      • Word Abbreviation
      • 1487. Making File Names Unique
      • 1365. How Many Numbers Are Smaller Than the Current Number
    • Presum
      • Longest Well-Performing Interval
      • 325. Maximum Size Subarray Sum Equals k
      • 525. Contiguous Array
      • Subarray Sum Equals K
    • Counting Sort
      • H-Index
    • Longest Consecutive Sequence
  • Multiple Pointers
    • 双指针之先后指针
      • 283. Move Zeroes
      • 27. Remove Element
      • 26. Remove Duplicates from Sorted Array
      • 80. Remove Duplicates from Sorted Array II
      • 228. Summary Ranges
      • 369. Plus One Linked List
      • 443. String Compression
      • 925. Long Pressed Name
    • Sliding Window
      • Static Size
        • 567. Permutation in String
        • Find All Anagrams in a String
        • 1297. Maximum Number of Occurrences of a Substring
        • Substring with Concatenation of All Words
        • Contains Duplicate III
        • 1456. Maximum Number of Vowels in a Substring of Given Length
      • Dynamic Window
        • Longest Substring Without Repeating Characters
        • 424. Longest Repeating Character Replacement
        • 1248. Count Number of Nice Subarrays
        • 340. Longest Substring with At Most K Distinct Characters
        • 395. Longest Substring with At Least K Repeating Characters
        • Minimum Window Substring
        • 1004. Max Consecutive Ones III
        • 1658. Minimum Operations to Reduce X to Zero
        • 209. Minimum Size Subarray Sum
    • 75. Sort Colors
    • 125. Valid Palindrome
      • Valid Palindrome II
    • Two Sum
      • 15. 3Sum
      • 1498. Number of Subsequences That Satisfy the Given Sum Condition
      • 16. 3Sum Closest
      • 4Sum
      • Sum of Square Numbers
      • 977. Squares of a Sorted Array
      • Container With Most Water
      • Trapping Rain Water
      • 259. 3Sum Smaller
      • 360. Sort Transformed Array
      • 611. Valid Triangle Number
    • Floyd Cycle
      • 202. Happy Number
      • 142. Linked List Cycle II
      • Linked List Cycle
      • 287. Find the Duplicate Number
    • Permutation
      • 31. Next Permutation
      • Previous Permutation
    • Zigzag Iterator
    • 632. Smallest Range Covering Elements from K Lists
    • Strobogrammatic Number
    • Quick Select
      • Kth Largest Element in an Array
      • K Closest Points
    • 349. Intersection of Two Arrays
      • 350. Intersection of Two Arrays II
  • Stack
    • Implement Queue by Two Stacks
    • 155. Min Stack
    • Implement Stack using Queues
    • 结合前面的输入
      • 20. Valid Parentheses
      • Evaluate Reverse Polish Notation
      • Baseball Game
      • 71. Simplify Path
      • Longest Absolute File Path
    • 维持递增或递减
      • 84. Largest Rectangle in Histogram
        • Maximal Rectangle
        • 1504. Count Submatrices With All Ones
      • Next Greater Element I
        • 503. Next Greater Element II
        • Next Greater Node In Linked List
      • Remove Duplicate Letters
      • 132 Pattern
    • Nested
      • 341. Flatten Nested List Iterator
      • 339. Nested List Weight Sum
      • Basic Calculator
      • Decode String
      • Mini Parser
      • 726. Number of Atoms
      • Exclusive Time of Functions
      • 227. Basic Calculator II
      • 772. Basic Calculator III
      • 1096. Brace Expansion II
    • Tree Traversal
      • Binary Tree Preorder Traversal
      • Path Sum II
      • Subtree of Another Tree
      • Binary Tree Inorder Traversal
      • Binary Tree Postorder Traversal
      • Binary Search Tree Iterator
      • Reconstruct Itinerary
      • Sum of Left Leaves
  • Breadth-first Search
    • Employee Importance
    • Remove Invalid Parentheses
    • Word Ladder II
    • 773. Sliding Puzzle
    • 407. Trapping Rain Water II
    • Level-order Traversal
      • Matrix Cells in Distance Order
      • Average of Levels in Binary Tree
      • Populating Next Right Pointers in Each Node II
      • Sum of Left Leaves
      • 107. Binary Tree Level Order Traversal II
      • Symmetric Tree
      • Find Bottom Left Tree Value
      • Find Largest Value in Each Tree Row
      • Add One Row to Tree
      • Binary Tree Right Side View
      • Binary Tree Zigzag Level Order Traversal
      • 1376. Time Needed to Inform All Employees
      • 1377. Frog Position After T Seconds
      • Clone Graph
      • index
        • 662. Maximum Width of Binary Tree
        • Binary Tree Vertical Order Traversal
        • 987. Vertical Order Traversal of a Binary Tree
        • Print Binary Tree
      • 267. Serialize and Deserialize Binary Tree
    • Letter Combinations of a Phone Number
    • 1197. Minimum Knight Moves
    • 247. Strobogrammatic Number II
    • 1298. Maximum Candies You Can Get from Boxes
    • 1311. Get Watched Videos by Your Friends
    • 1391. Check if There is a Valid Path in a Grid
    • 815. Bus Routes
    • 扫格
      • Walls and Gates
      • Minesweeper
      • 01 Matrix
      • 1293. Shortest Path with Obstacles Elimination
      • Pacific Atlantic Water Flow
      • The Maze II
      • The Maze
      • The Maze III
      • 1036. Escape a Large Maze
      • 317. Shortest Distance from All Buildings
    • Topological Sort
      • Course Schedule
      • 210. Course Schedule II
      • Build Robot
      • 269. Alien Dictionary
        • 953. Verifying an Alien Dictionary
  • Bit Manipulation
    • XOR
      • Single Number
      • 137. Single Number II
      • 260. Single Number III
      • Set Mismatch
      • Missing Number
      • 1310. XOR Queries of a Subarray
      • 1442. Count Triplets That Can Form Two Arrays of Equal XOR
      • Find the Difference
      • Hamming Distance
      • Maximum XOR of Two Numbers in an Array
    • Hash
      • Repeated DNA Sequences
    • AND
      • Power of Two
      • 201. Bitwise AND of Numbers Range
    • Total Hamming Distance
    • 190. Reverse Bits
  • Math
    • Geometry
      • Largest Triangle Area
      • 593. Valid Square
    • Count Primes
    • 441. Arranging Coins
    • Permutation Sequence
    • Range Addition II
    • 进制转换
      • Excel Sheet Column Title
      • Excel Sheet Column Number
      • 405. Convert a Number to Hexadecimal
      • 660 Remove 9
    • Maximum Product of Three Numbers
    • Power of Three
    • Ugly Number
    • 1344. Angle Between Hands of a Clock
    • 66. Plus One
    • 780. Reaching Points
    • 564. Find the Closest Palindrome
    • Sqrt(x)
      • Valid Perfect Square
      • 1390. Four Divisors
    • Factorial Trailing Zeroes
    • Strobogrammatic Number
    • 296. Best Meeting Point
    • 排列组合
      • 1643. Kth Smallest Instructions
    • Perfect Number
    • 加法
      • 67. Add Binary
      • Add Strings
      • Multiply Strings
    • Nth Digit
    • Roman to Integer
      • Integer to Roman
      • Integer to English Words
    • Pow(x, n)
    • Divide Two Integers
    • GCD
    • Geometry
      • Max Points on a Line
      • Rectangle Area
      • Line Reflection
    • Super Pow
    • 829. Consecutive Numbers Sum
    • 找规律
      • Rotate Function
      • Bulb Switcher
      • Add Digits
      • 1247. Minimum Swaps to Make Strings Equal
      • Bulb Switcher II
      • 1503. Last Moment Before All Ants Fall Out of a Plank
    • Next Closest Time
    • 1362. Closest Divisors
    • Missing Ranges
    • Strobogrammatic Number III
    • 1154. Day of the Year
    • 1360. Number of Days Between Two Dates
    • Majority Element
      • Majority Element II
    • 311. Sparse Matrix Multiplication
    • Maximum Swap
    • Reservoir Sampling
      • Random Pick Index
      • 382. Linked List Random Node
    • Integer Break
    • Largest Perimeter Triangle
    • 1363. Largest Multiple of Three
    • Binary Prefix Divisible By 5
    • 随机数
      • 470. Implement Rand10() Using Rand7()
      • 478. Generate Random Point in a Circle
      • 528. Random Pick with Weight
      • 710. Random Pick with Blacklist
      • 381. Insert/Del GetRandom O(1)-Duplicates allowed
  • Trie
    • Replace Words
    • 208. Implement Trie (Prefix Tree)
    • 211. Add and Search Word - Data structure design
      • Add and Search Word with Regular Expression - Data structure design
    • 1032. Stream of Characters
    • 745. Prefix and Suffix Search
    • Word Search II
    • 425. Word Squares
    • 642. Design Search Autocomplete System
  • Graph
    • 1192. Critical Connections in a Network
    • 1466. Reorder Routes to Make All Paths Lead to the City Zero
    • 1786. Number of Restricted Paths From First to Last Node
    • 1514. Path with Maximum Probability
    • Bipartition
      • Possible Bipartition
      • Is Graph Bipartite?
  • Union Find
    • 200. Number of Islands
    • 130. Surrounded Regions
    • Friend Circles
    • 947. Most Stones Removed with Same Row or Column
    • Graph Valid Tree
    • 1202. Smallest String With Swaps
    • 721. Accounts Merge
    • Minimize Malware Spread
      • Minimize Malware Spread II
    • Satisfiability of Equality Equations
    • Number of Enclaves
    • 803. Bricks Falling When Hit
    • 685. Redundant Connection II
    • 839. Similar String Groups
    • 305. Number of Islands II
  • Exhaustive Search
    • 78. Subsets
    • 90. Subsets II
    • Permutations
    • Permutations II
    • Partition to K Equal Sum Subsets
      • 216. Combination Sum III
    • 79. Word Search
    • 140. Word Break II
    • 291. Word Pattern II
    • Expression Add Operators
    • Android Unlock Patterns
    • Shopping Offers
    • Binary Watch
    • Generalized Abbreviation
    • 运算
      • Evaluate Division
      • 679. 24 Game
      • 536. Construct Binary Tree from String
      • 736. Parse Lisp Expression
    • 301. Remove Invalid Parentheses
      • 1249. Minimum Remove to Make Valid Parentheses
      • 921. Minimum Add to Make Parentheses Valid
      • 678. Valid Parenthesis String
    • Number of Islands
    • 51. N-Queens
      • 489. Robot Room Cleaner
    • 37. Sudoku Solver
    • 248. Strobogrammatic Number III
    • 1066. Campus Bikes II
    • 691. Stickers to Spell Word
    • 1284. Minimum Number of Flips to Convert Binary Matrix to Zero Matrix
    • 753. Cracking the Safe
    • 1706. Where Will the Ball Fall
    • 465. Optimal Account Balancing
  • String
    • Repeated String Match
    • 13. Roman to Integer
    • String to Integer (atoi)
    • 1451. Rearrange Words in a Sentence
    • Judge Route Circle
    • Remove Comments
    • Count and Say
    • Sentence Screen Fitting
    • Encode and Decode Strings
    • Add Bold Tag in String
    • Group Shifted Strings
    • Valid Word Square
    • 794. Valid Tic-Tac-Toe State
    • 348. Design Tic-Tac-Toe
    • Valid Number
    • Read N Characters Given Read4
      • Read N Characters Given Read4 II - Call multiple times
    • One Edit Distance
    • Restore IP Addresses
    • 468. Validate IP Address
    • 440. K-th Smallest in Lexicographical Order
    • Bold Words in String
    • 1417. Reformat The String
    • 824. Goat Latin
    • License Key Formatting
  • Greedy
    • 1785. Minimum Elements to Add to Form a Given Sum
    • 122. Best Time to Buy and Sell Stock II
    • 45. Jump Game II
    • 55. Jump Game
    • 452. Minimum Number of Arrows to Burst Balloons
    • 871. Minimum Number of Refueling Stops
    • Task Scheduler
    • 768. Max Chunks To Make Sorted II
    • Non-overlapping Intervals
    • 670. Maximum Swap
    • Binary Tree Cameras
    • 135. Candy
    • 358. Rearrange String k Distance Apart
    • 767. Reorganize String
    • 1057. Campus Bikes
    • 936. Stamping The Sequence
    • 1296. Divide Array in Sets of K Consecutive Numbers
    • 1342. Reduce Array Size to The Half
    • 1353. Maximum Number of Events That Can Be Attended
    • 1488. Avoid Flood in The City
    • 1647. Minimum Deletions to Make Character Frequencies Unique
    • 1648. Sell Diminishing-Valued Colored Balls
    • 1665. Minimum Initial Energy to Finish Tasks
  • Design
    • Peeking Iterator
    • Insert Delete GetRandom O(1)
    • Flatten 2D Vector
  • Queue
    • Design Hit Counter
    • 622. Design Circular Queue
    • Moving Average from Data Stream
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  1. Dynamic Programming I

DFS + Memorization

用于无法直接写出递推式的。

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