算法题精选(Leetcode/Codeforce)

个人刷算法题的做题笔记和心得，收录了个人认为典型或有趣的题目。

更新中... 2023

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Bit Manipulation

• 136. Single Number

• 137. Single Number II

• 260. Single Number III

• 191. Number of 1 Bits

• 268. Missing Number

• 231. Power of Two

• 191. Number of 1 Bits

• 2275. Largest Combination With Bitwise AND Greater Than Zero

• 2419. Longest Subarray With Maximum Bitwise AND (non-increasing means a[i] >= a[i + 1], non-decreasing is the same logic)

• 2425. Bitwise XOR of All Pairings

• 2397. Maximum Rows Covered by Columns (位运算遍历所有可能)

• 2527. Find Xor-Beauty of Array

• 2411. Smallest Subarrays With Maximum Bitwise OR (或运算|与最值)

• 1734. Decode XORed Permutation (XOR运算的’交换律‘)

• 2564. Substring XOR Queries (XOR+常识)

• 2568. Minimum Impossible OR

• 1915. Number of Wonderful Substrings (preSum + bitmask)

• 1178. Number of Valid Words for Each Puzzle (bitmask)

• 1542. Find Longest Awesome Substring (bitmask + prefix)

• 2680. Maximum OR (bit OR)

• 2749. Minimum Operations to Make the Integer Zero (bit / brainteaser)

• 2528. Maximize the Minimum Powered City (二分+差分)

• 2772. Apply Operations to Make All Array Elements Equal to Zero (差分数组)

• 2857. Count Pairs of Points With Distance k (枚举 / thinking)

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Array

• 54. Spiral Matrix

• 59. Spiral Matrix II

• 33. Search in Rotated Sorted Array

• 11. Container With Most Water

• 560. Subarray Sum Equals K(累加和)

• 1018. Binary Prefix Divisible By 5

• 56. Merge Intervals

• 42. Trapping Rain Water (DP/单调栈)

• 41. First Missing Positive

• 442. Find All Duplicates in an Array

• 525. Contiguous Array * (preSum + hash)

• 523. Continuous Subarray Sum

• 2488. Count Subarrays With Median K

• 2453. Destroy Sequential Targets (%号分组)

• 452. Minimum Number of Arrows to Burst Balloons (interval类型题目)

• 53. Maximum Subarray (kadane/DP/分治法)

• 918. Maximum Sum Circular Subarray (kadane算法)

• 974. Subarray Sums Divisible by K (前缀和/Map)

• 2449. Minimum Number of Operations to Make Arrays Similar (Sort/Greedy)

• 315. Count of Smaller Numbers After Self (树状数组)

• 2563. Count the Number of Fair Pairs (排序+two pointers/二分)

• 1871. Jump Game VII (preSum/sliding)

• 2584. Split the Array to Make Coprime Products (Array/Map)

• 2444. Count Subarrays With Fixed Bounds (Sliding Window / Subarray / Three Pointers)

• 2588. Count the Number of Beautiful Subarrays (XOR / preSum)

• 2589. Minimum Time to Complete All Tasks (Interval / Sorting / Greedy)

• 2348. Number of Zero-Filled Subarrays (Omit)

• 2597. The Number of Beautiful Subsets (Subset / Hash / Set / Math)

• 2607. Make K-Subarray Sums Equal (Circluar Array / Median)

• 2536. Increment Submatrices by One / LCP 74. 最强祝福力场 (离散化+二维差分)

• 2653. Sliding Subarray Beauty / 1419. Minimum Number of Frogs Croaking (Counting)

• 2718. Sum of Matrix After Queries (矩阵操作 / 倒序)

• 2731. Movement of Robots (robots碰撞 / 思维题)

• 2735. Collecting Chocolates (思维题)

• 1186. Maximum Subarray Sum with One Deletion (sliding window ? kadane!)

• Codeforces Round 881 (Div.3) F1. Omsk Metro (simple version) (Kadane / DP)

• 2779. Maximum Beauty of an Array After Applying Operation (排序 + 滑动窗口 / 差分)

• 2842. Count K-Subsequences of a String With Maximum Beauty (组合数学C/A)

• 2963. Count the Number of Good Partitions (区间)

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Binary Search

• 2517. Maximum Tastiness of Candy Basket (二分题型方法总结)

• 2226. Maximum Candies Allocated to K Children

• 2250. Count Number of Rectangles Containing Each Point

• 2448. Minimum Cost to Make Array Equal

• 2513. Minimize the Maximum of Two Arrays (二分+集合计算)

• 2576. Find the Maximum Number of Marked Indices (二分+贪心 / 双指针)

• 2616. Minimize the Maximum Difference of Pairs (二分+贪心+数学归纳法)

• 1498. Number of Subsequences That Satisfy the Given Sum Condition / 1964. Find the Longest Valid Obstacle Course at Each Position (Binary Search in Array)

• 1760. Minimum Limit of Balls in a Bag (10^9二分后是多少？)

• Codeforces Round 881 E. Tracking Segments

• 69. Sqrt(x) (某du外包题)

• 2856. Minimum Array Length After Pair Removals (贪心 / 二分)

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Top K

• 215. Kth Largest Element in an Array

• 347. Top K Frequent Elements

• 703. Kth Largest Element in a Stream

• 1383. Maximum Performance of a Team / 502. IPO (Heap/Sort)

• 2551. Put Marbles in Bags (两端数之和/Heap)

• 2813. Maximum Elegance of a K-Length Subsequence (堆/排序)

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Linkedlist

• 206. Reverse Linked List

• 148. Sort List

• 109. Convert Sorted List to Binary Search Tree

• 2487. Remove Nodes From Linked List

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Stack & Queue

• 20. Valid Parentheses

• 1209. Remove All Adjacent Duplicates in String II

• 456. 132 Pattern

• 739. Daily Temperatures

• 901. Online Stock Span

• 2375. Construct Smallest Number From DI String

• 2289. Steps to Make Array Non-decreasing (单调栈/dp)

• 85. Maximal Rectangle (单调栈/DP)

• 1124. Longest Well-Performing Interval (单调栈/哈希)

• 1856. Maximum Subarray Min-Product (Monotonic Stack单调栈 / 单调栈+贡献法汇总)

• 649. Dota2 Senate (Simulation + Queue)

• 735. Asteroid Collision & 2751. Robot Collisions (Stack / Movement)

• 2818. Apply Operations to Maximize Score (单调栈 + 贡献法 + 质因数 + 快速幂)

• 2866. Beautiful Towers II (单调栈 + 前后缀分解)

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Sliding Window & Two Pointers

• 209. Minimum Size Subarray Sum

• 3. Longest Substring Without Repeating Characters

• 76. Minimum Window Substring

• 239. Sliding Window Maximum (堆/单调队列/分组预处理)

• 424. Longest Repeating Character Replacement

• 81. Search in Rotated Sorted Array II(Binary Search)

• 2271. Maximum White Tiles Covered by a Carpet

• 2401. Longest Nice Subarray (滑动窗口/位运算)

• 2516. Take K of Each Character From Left and Right

• 2537. Count the Number of Good Subarrays (滑动窗口/可逆向思维/子数组数量变化计算)

• 2234. Maximum Total Beauty of the Gardens (Sorting/Two Pointers)

• 1793. Maximum Score of a Good Subarray (Greedy + Two pointers)

• 2747. Count Zero Request Servers (Sort + Sliding Window)

• 1838. Frequency of the Most Frequent Element (Cnt + Greedy + Sliding Window)

• 719. Find K-th Smallest Pair Distance (Binary Search + Sliding Window)

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String

• 8. String to Integer (atoi)

• 43. Multiply Strings

• 179. Largest Number

• 2472. Maximum Number of Non-overlapping Palindrome Substrings (贪心+DP)

• 2484. Count Palindromic Subsequences (奇数次Palindromic String DP)

• 2663. Lexicographically Smallest Beautiful String (palindrome + greedy + 思维题)

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BFS/DFS

• 200. Number of Islands

• 695. Max Area of Island *

• 114. Flatten Binary Tree to Linked List

• 337. House Robber III

• 116. Populating Next Right Pointers in Each Node

• 1091. Shortest Path in Binary Matrix

• 329. Longest Increasing Path in a Matrix

• 2328. Number of Increasing Paths in a Grid (DFS+记忆化搜索/多源BFS+优先队列)

• 2477. Minimum Fuel Cost to Report to the Capital

• 433. Minimum Genetic Mutation

• 2503. Maximum Number of Points From Grid Queries (BFS+presum)

• 2290. Minimum Obstacle Removal to Reach Corner (BFS/PQ)

• 1976. Number of Ways to Arrive at Destination (BFS+PQ/Dijkstra)

• 1162. As Far from Land as Possible (BFS/DP)

• 2556. Disconnect Path in a Binary Matrix by at Most One Flip (DFS/路径覆盖)

• 1345. Jump Game IV (BFS in Array)

• 2612. Minimum Reverse Operations (BFS in Array / TreeSet)

• 934. Shortest Bridge (BFS/DFS/visited)

• 1631. Path With Minimum Effort (多源BFS)

• 847. Shortest Path Visiting All Nodes

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Backtracking

• 46. Permutations **

• 77. Combinations

• 78. Subsets

• 39. Combination Sum

• 40. Combination Sum II

• 140. Word Break II

• 79. Word Search

• 208. Implement Trie (Prefix Tree)(Trie)

• 212. Word Search II(Trie)

• 2698. Find the Punishment Number of an Integer (Backtracking + 预处理)

• 421. Maximum XOR of Two Numbers in an Array (Trie)

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Greedy

• 55. Jump Game

• 45. Jump Game II

• 1337. The K Weakest Rows in a Matrix

• 2406. Divide Intervals Into Minimum Number of Groups (intervals/sort/greedy)

• 2434. Using a Robot to Print the Lexicographically Smallest String

• 334. Increasing Triplet Subsequence

• 2498. Frog Jump II

• 2178. Maximum Split of Positive Even Integers

• 2086. Minimum Number of Food Buckets to Feed the Hamsters (辐射)

• 1605. Find Valid Matrix Given Row and Column Sums (二维数组/贪心)

• 1899. Merge Triplets to Form Target Triplet (Greedy)

• 2967. Minimum Cost to Make Array Equalindromic (Greedy + Math + Binary Search)

• Codeforces Round 913 (Div.3) C. Removal of Unattractive Pairs (Greedy)

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Tree

• 98. Validate Binary Search Tree

• 235. Lowest Common Ancestor of a Binary Search Tree

• 617. Merge Two Binary Trees

• 103. Binary Tree Zigzag Level Order Traversal

• 94. Binary Tree Inorder Traversal

• 96. Unique Binary Search Trees

• 222. Count Complete Tree Nodes

• 2458. Height of Binary Tree After Subtree Removal Queries

• 1443. Minimum Time to Collect All Apples in a Tree (多叉树的深度遍历)

• 124. Binary Tree Maximum Path Sum (树的path问题/dfs)

• 2385. Amount of Time for Binary Tree to Be Infected (同样是path问题/dfs)

• 2538. Difference Between Maximum and Minimum Price Sum (rerooting/DFS缓存)

• 968. Binary Tree Cameras (树状DP)

• 2581. Count Number of Possible Root Nodes (rerooting/twice DFS)

• 2392. Build a Matrix With Conditions (拓扑排序)

• 2603. Collect Coins in a Tree (Topological Sort 拓扑排序 总)

• 1026. Maximum Difference Between Node and Ancestor (递/归两种dfs)

• 2646. Minimize the Total Price of the Trips (树形DP)

• 2673. Make Costs of Paths Equal in a Binary Tree (树上DFS/归并贪心)

• 2858. Minimum Edge Reversals So Every Node Is Reachable (rerooting / 换根DP)

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Graph

• 1584. Min Cost to Connect All Points (图的两种经典算法：Prim、Kruskal+UnionFind)

• 785. Is Graph Bipartite?

• 1202. Smallest String With Swaps

• 547. Number of Provinces

• 1192. Critical Connections in a Network(Tarjan algorithm)

• 2374. Node With Highest Edge Score

• 2467. Most Profitable Path in a Tree

• 2492. Minimum Score of a Path Between Two Cities

• 1697. Checking Existence of Edge Length Limited Paths (树或图的path问题/Union Find 汇总)

• 2421. Number of Good Paths (树或图path问题/并查集+数学+排序连接)

• 2608. Shortest Cycle in a Graph / 2360. Longest Cycle in a Graph (无向图或有向图中的计算环长度问题/DFS或BFS)

• 2642. Design Graph With Shortest Path Calculator (有向权值图中两点最短路径)

• 1579. Remove Max Number of Edges to Keep Graph Fully Traversable (Union Find + 分类 + 删除/贪心)

• 2662. Minimum Cost of a Path With Special Roads (朴素Dijkstra)

• 2709. Greatest Common Divisor Traversal (素数筛 + 并查集)

• 1483. Kth Ancestor of a Tree Node / 2836. Maximize Value of Function in a Ball Passing Game (树上倍增)

• 2846. Minimum Edge Weight Equilibrium Queries in a Tree (LCA模版)

• 2850. Minimum Moves to Spread Stones Over Grid (全排列)

• 2876. Count Visited Nodes in a Directed Graph (内向基环树 / 拓扑排序)

• 2867. Count Valid Paths in a Tree (DFS / 并查集 / 染色)

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DP

• 746. Min Cost Climbing Stairs

• 64. Minimum Path Sum

• 322. Coin Change

• 931. Minimum Falling Path Sum

• 70. Climbing Stairs

• 62. Unique Paths

• 1155. Number of Dice Rolls With Target Sum

• 300. Longest Increasing Subsequence(LIS问题)

• 354. Russian Doll Envelopes(LIS问题)

• 646. Maximum Length of Pair Chain (LIS/Greedy)

• 1143. Longest Common Subsequence

• 120. Triangle

• 518. Coin Change 2

• 5. Longest Palindromic Substring

• 236. Lowest Common Ancestor of a Binary Tree

• 543. Diameter of Binary Tree

• 233. Number of Digit One

• 121. Best Time to Buy and Sell Stock

• 122. Best Time to Buy and Sell Stock II

• 198. House Robber

• 873. Length of Longest Fibonacci Subsequence

• 674. Longest Continuous Increasing Subsequence

• 494. Target Sum

• 647. Palindromic Substrings

• 152. Maximum Product Subarray

• 213. House Robber II

• 10. Regular Expression Matching

• 32. Longest Valid Parentheses

• 687. Longest Univalue Path

• 139. Word Break

• 174. Dungeon Game

• 416. Partition Equal Subset Sum **

• 91. Decode Ways

• 1029. Two City Scheduling

• 740. Delete and Earn

• 1884. Egg Drop With 2 Eggs and N Floors

• 72. Edit Distance

• 583. Delete Operation for Two Strings

• 1937. Maximum Number of Points with Cost

• 1035. Uncrossed Lines

• 2262. Total Appeal of A String *

• 115. Distinct Subsequences

• 2266. Count Number of Texts *

• 1641. Count Sorted Vowel Strings * *

• 474. Ones and Zeroes(DP解决subset问题)

• 2140. Solving Questions With Brainpower

• 2305. Fair Distribution of Cookies(状态压缩DP/用位表示)

• 2311. Longest Binary Subsequence Less Than or Equal to K (LIS)

• 2327. Number of People Aware of a Secret

• 2400. Number of Ways to Reach a Position After Exactly k Steps (在数轴上移动DP)

• 2435. Paths in Matrix Whose Sum Is Divisible by K

• 2518. Number of Great Partitions (coin change/knapsack背包)

• 926. Flip String to Monotone Increasing / 1653. Minimum Deletions to Make String Balanced (前缀和 / 01 string DP)

• 131. Palindrome Partitioning (Palindrome/DP/Backtrack)

• 2547. Minimum Cost to Split an Array (coin change的变型)

• 2552. Count Increasing Quadruplets (三元组/四元组/DP/元素在n范围内)

• 1626. Best Team With No Conflicts (Sorting/DP)

• 1727. Largest Submatrix With Rearrangements (Sorting/DP)

• 1911. Maximum Alternating Subsequence Sum (DP/Greedy)

• 123. Best Time to Buy and Sell Stock III / 2555. Maximize Win From Two Segments (DP/Sliding Window)

• 2054. Two Best Non-Overlapping Events / 1235. Maximum Profit in Job Scheduling (二分/自顶向下DP/记忆化搜索/)

• 2572. Count the Number of Square-Free Subsets (DP+bitmask)

• 1986. Minimum Number of Work Sessions to Finish the Tasks (DP+bitmask+dfs)

• 2585. Number of Ways to Earn Points (Knapsack / Limited Coin Change)

• 1012. Numbers With Repeated Digits (Digit DP 数位DP / Memorize Search / DFS)

• 1553. Minimum Number of Days to Eat N Oranges (Memoization+DFS 记忆化搜索)

• 1000. Minimum Cost to Merge Stones (区间DP)

• 2218. Maximum Value of K Coins From Piles (Top-down DP / Memoization)

• 1187. Make Array Strictly Increasing / 1043. Partition Array for Maximum Sum (Memoization -> DP 汇总)

• 940. Distinct Subsequences II / 1987. Number of Unique Good Subsequences (String Subsequences / DP / Ends)

• 2681. Power of Heroes (DP)

• 2708. Maximum Strength of a Group (top-down dp + 乘法 / Greedy)

• 2712. Minimum Cost to Make All Characters Equal (01 String DP / Greedy)

• 2713. Maximum Strictly Increasing Cells in a Matrix (多源DP + 优先队列排序)

• 1262. Greatest Sum Divisible by Three (Greedy + Reverse / DP)

• 2741. Special Permutations (Permulation DP 全排列DP)

• 956. Tallest Billboard (Memoization DFS / DP)

• 2750. Ways to Split Array Into Good Subarrays (Greedy / DP)

• 2787. Ways to Express an Integer as Sum of Powers (背包)

• 2791. Count Paths That Can Form a Palindrome in a Tree (状压+前缀和哈希 / 树)

• 486. Predict the Winner / 464. Can I Win (Game Theory / DFS / Memoization)

• 2830. Maximize the Profit as the Salesman (二分DP / 同1235)

• 97. Interleaving String (自己重新做一遍)

• 2919. Minimum Increment Operations to Make Array Beautiful

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Others

• 146. LRU Cache (LRU/LFU)

• 69. Sqrt(x)

• 50. Pow(x, n) (2的倍数可以通过左移/右移位数来实现)

• 204. Count Primes

• 2280. Minimum Lines to Represent a Line Chart(double精度问题/最大公约数)

• 2353. Design a Food Rating System

• 2364. Count Number of Bad Pairs (Hash)

• 2447. Number of Subarrays With GCD Equal to K (最大公约数)

• 1760D Challenging Valleys (状态机)

• 2499. Minimum Total Cost to Make Arrays Unequal (数学)

• 2532. Time to Cross a Bridge (模拟题)

• 2402. Meeting Rooms III (模拟题)

• 2543. Check if Point Is Reachable (点能否到点的问题/找规律/数学)

• 2550. Count Collisions of Monkeys on a Polygon (快速幂)

• 1250. Check If It Is a Good Array (扩展欧几里得定理/裴蜀定理)

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