Coding Practice

Coding parctice based on LeetCode and Coding Interview book,
including algorithm, database, shell, concurrency problems and other online contests.

Category

• LeetCode
  • Algorithms
  • Database
  • Shell
  • Concurrency
• CodingInterview
• Contest
  • LeetCode Contest
  • KickStart Contest
• Acknowledgments
• Feedback

LeetCode

Algorithms

#	Title Difficulty	Category Solution	Notes
1	Two Sum Easy	Math Array Python3	枚举 哈希表
2	Add Two Numbers Medium	Math LinkedList Python3	模拟
3	Longest Substring Without Repeating Characters Medium	String Substring Python3	滑动窗口
4	Median of Two Sorted Arrays Hard	Array DevideAndConquer Python3	👊✔️ 模拟 归并排序 二分
5	Longest Palindromic Substring Medium	String Palindrome Python3	中心扩散法 DP
6	ZigZag Conversion Medium	String Python3	模拟 找规律
7	Reverse Integer Easy	Math Python3	转化为字符串 模拟
8	String to Integer (atoi) Medium	Math Python3	模拟
9	Palindrome Number Easy	String Palindrome Python3	转化为字符串 模拟
10	Regular Expression Matching Hard	DynamicProgramming Python3	✊☑️ 递归 DP
11	Container With Most Water Medium	Math, Array Python3
12	Integer to Roman Medium	String Python3
13	Roman to Integer Easy	String Python3
14	Longest Common Prefix Easy	String Python3
15	3Sum Medium	Math Sum Python3	双指针法
16	3Sum Closest Medium	Math Sum Python3
17	Letter Combinations of a Phone Number Medium	BackTracking Enumeration Python3	递归回溯
18	4Sum Medium	Math Sum Python3
19	Remove Nth Node From End of List Medium	LinkedList Python3
20	Valid Parentheses Easy	String Parentheses Python3
21	Merge Two Sorted Lists Easy	LinkedList Python3
22	Generate Parentheses Medium	String Parentheses Python3
23	Merge k Sorted Lists Hard	LinkedList Python3
24	Swap Nodes in Pairs Medium	LinkedList Python3	dummynode 找规律
25	Reverse Nodes in k-Group Hard	LinkedList Python3	翻转拼接
26	Remove Duplicates from Sorted Array Easy	Array Python3	双指针移动
27	Remove Element Easy	Array Python3
28	Implement strStr() Easy	String Python3	字符串匹配 KMP算法
29	Divide Two Integers Medium	Math Python3	尽可能多减
30	Substring with Concatenation of All Words	String Hard Python3	两种实现
31	Next Permutation Medium	Array Python3	规律模拟
32	Longest Valid Parentheses Hard	String DynamicProgramming Python3	👍✅😍 暴力枚举 栈模拟 动态规划 双向扫描
33	Search in Rotated Sorted Array Medium	Binary Search Python3
34	Find First and Last Position of Element in Sorted Array Medium	Binary Search Python3	构造二分性 >=target <=target
35	Search Insert Position Easy	Array Python3	折半查找 找到 越界返回
36	Valid Sudoku Medium	BackTracking Python3	👍 row,col,cube判重
37	Sudoku Solver Hard	BackTracking Python3	👍 ✅
38	Count and Say Easy	String Python3
39	Combination Sum Medium	BackTracking Python3
40	Combination Sum II Medium	BackTracking Python3	排序 跳过重复元素
41	First Missing Positive Hard	Array Python3	👍 桶排序
42	Trapping Rain Water Hard	Array TwoPointers Stack Python3	👍✅ 多次线性扫描 双指针
43	Multiply Strings Medium	Math String Python3	👍 模拟 竖式乘法 大数相乘
44	Wildcard Matching Hard	String DynamicProgramming BackTracking Greedy Python3	☑️😍👍🔝 DP 双指针模拟
45	Jump Game II Hard	Array Greedy Python3	👍 贪心
46	Permutations Medium	BackTracking Python3	DFS+回溯
47	Permutations II Medium	BackTracking Python3	排序，跳过重复元素
48	Rotate Image Medium	Array Math Python3	👍 操作分解
49	Group Anagrams Medium	String Python3	三种方法求解
50	Pow(x, n) Medium	Math BinarySearch Python3	库函数 蛮力法 二分法
51	N-Queens Medium	BackTracking Python3	👍 ✅
52	N-Queens II Hard	BackTracking Python3	👍 ✅
53	Maximum Subarray Easy	Array Python3
54	Spiral Matrix Medium	Matrix Python3	过程模拟 边界处理 标记已访问
55	Jump Game Medium	Array Greedy Python3	👍 贪心
56	Merge Intervals Medium	Sort Python3	先排序后合并
57	Insert Interval Hard	Array Sort Python3	👍✅ 区间合并
58	Length of Last Word Easy	String Python3	长度之差
59	Spiral Matrix II Medium	Array Python3	简单模拟
60	Permutation Sequence Medium	Math BackTracking Python3	👍🔝✅ based on 46 based on 31 规律模拟
61	Rotate List Medium	LinkedList Python3	双指针定边界
62	Unique Paths Medium	Array DynamicProgramming Python3	👍✅ 递归 记忆递归 DP DP空间优化 组合数学
63	Unique Paths II Medium	Array DynamicProgramming Python3	👍✅ 动态规划
64	Minimum Path Sum Medium	Array DynamicProgramming Python3	普通DP 待优化
65	Valid Number Hard	Math String Python3	👍 正则 模拟
66	Plus One Easy	Array Python3	模拟
67	Add Binary Easy	Math String Python3	逐位处理
68	Text Justification Hard	String Python3	✅ 模拟 逐行处理拼接
69	Sqrt(x) Easy	Math Python3	二分查找
70	Climbing Stairs Medium	DynamicProgramming Python3
71	Simplify Path Medium	String Stack Python3	👍 栈的应用
72	Edit Distance Hard	DynamicProgramming Python3	👍✅ 最小编辑距离
73	Set Matrix Zeroes Medium	Array Python3	分配资源再利用 Trick
74	Search a 2D Matrix Medium	BinarySearch Python3	构造两段性
75	Sort Colors Medium	Sort Python3	👍 计数排序 冒泡排序 三指针法
76	Minimum Window Substring Hard	HashTable TwoPointers String Sliding Window Python3	👍✅ 滑动窗口
77	Combinations Medium	BackTracking Python3	DFS回溯
78	Subsets Medium	BackTracking Python3	递归 非递归
79	Word Search Medium	Search BackTracking Array Python3	👍 DFS
80	Remove Duplicates from Sorted Array II Medium	Array TwoPointers Python3	双指针遍历
81	Search in Rotated Sorted Array II Medium	Array BinarySearch Python3	🔝👍 两种二分写法
82	Remove Duplicates from Sorted List II Medium	LinkedList Python3	递归 双指针
83	Remove Duplicates from Sorted List Easy	LinkedList Python3
84	Largest Rectangle in Histogram Hard	Array Stack Python3	👍✅ 单调栈
85	Maximal Rectangle Hard	Array HashTable DynamicProgramming Stack Python3	👍✅ 单调栈 84题扩展
86	Partition List Medium	LinkedList TwoPointers Python3	模拟 双指划分合并
87	Scramble String Hard	BinaryTree Python3	递归暴力搜索
88	Merge Sorted Array Easy	Array Python3	线性合并
89	Gray Code Medium	BackTracking Python3	✅ 规律递归
90	Subsets II Medium	BackTracking Python3	78+过滤
91	Decode Ways Medium	DynamicProgramming String Python3	DP
92	Reverse Linked List II Medium	LinkedList Python3	206变体
93	Restore IP Addresses Medium	String BackTracking Python3	👍 DFS递归 处理前缀0
94	Binary Tree Inorder Traversal Medium	BinaryTree Stack Python3	递归 迭代
95	Unique Binary Search Trees II Medium	DynamicProgramming BinarySearchTree Python3	👍😈
96	Unique Binary Search Trees Medium	DynamicProgramming BinarySearchTree Python3	👍 DP Catalan number
97	Interleaving String Hard	DynamicProgramming String Python3	👍 DP
98	Validate Binary Search Tree Medium	BinarySearchTree DFS Python3	DFS 中序遍历
99	Recover Binary Search Tree Hard	BinarySearchTree Python3	👍☑️ Morris-traversal
100	Same Tree Easy	BinaryTree Python3	递归判断
101	Symmetric Tree Easy	BinaryTree DFS Python3	递归 迭代
102	Binary Tree Level Order Traversal Medium	BinaryTree BFS Python3	BFS逐层操作
103	Binary Tree Zigzag Level Order Traversal Medium	Stack BinaryTree BFS Python3	BFS模拟
104	Maximum Depth of Binary Tree Easy	BinaryTree Python3	基本递归
105	Construct Binary Tree from Preorder and Inorder Traversal Medium	BinaryTree DFS Python3	递归基本操作
106	Construct Binary Tree from Inorder and Postorder Traversal Medium	BinaryTree Array DFS Python3	递归模拟
107	Binary Tree Level Order Traversal II Easy	BinaryTree BFS Python3	BFS模拟 逆序输出
108	Convert Sorted Array to Binary Search Tree Easy	BinaryTree DFS Python3	递归中序遍历
109	Convert Sorted List to Binary Search Tree Medium	LinkedList DFS Python3	root节点的查找
110	Balanced Binary Tree Easy	BinaryTree DFS Python3	递归枚举 置标志位优化
111	Minimum Depth of Binary Tree Easy	BinaryTree DFS BFS Python3	👍🔝 递归DFS 栈DFS 队列BFS
112	Path Sum Easy	BinaryTree DFS Python3	简单递归
113	Path Sum II Medium	BinaryTree DFS Python3	DFS递归
114	Flatten Binary Tree to Linked List Medium	BinaryTree DFS Python3	👍🔝☑️ 递归 迭代 非迭代
115	Distinct Subsequences Hard	String DynamicProgramming Python3	☑️🔝 DP
116	Populating Next Right Pointers in Each Node Medium	BinaryTree Python3	BFS O(1)Space
117	Populating Next Right Pointers in Each Node II Medium	BinaryTree Python3	BFS O(n)Space
118	Pascal's Triangle Medium	Array Python3	模拟生成
119	Pascal's Triangle II Easy	Array Python3	👍✅🔝😍 双行模拟 单行自后向前
120	Triangle Medium	Array DynamicProgramming Python3	DP
121	Best Time to Buy and Sell Stock Easy	Math Array DynamicProgramming Python3
122	Best Time to Buy and Sell Stock II Easy	Greedy Python3	贪心策略总结
123	Best Time to Buy and Sell Stock III Hard	DynamicProgramming Python3	👍✅ 贪心 DP
124	Binary Tree Maximum Path Sum Hard	BinaryTree Python3	👍 DFS
125	Valid Palindrome Easy	String TwoPointers Python3	正则 双指针线性扫描
126	Word Ladder II Hard	Array String BackTracking BFS Python3	👍🔝☑️ 双向BFS+hash
127	Word Ladder Medium	BFS Python3	🔝☑️ BFS 双向BFS
128	Longest Consecutive Sequence Hard	Array Greedy Python3	👍 哈希
129	Sum Root to Leaf Numbers Medium	BinaryTree DFS Python3	👍😍 迭代 递归 Morris-traversal
130	Surrounded Regions Medium	DFS BFS UnionFind Python3	👍 BFS 逆向考虑
131	Palindrome Partitioning Medium	String BackTracking Python3	DFS 回溯 DP(TODO)
133	Clone Graph Medium	Graph BFS DFS Python3	set去重
134	Gas Station Medium	Greddy Array Python3	贪心双指针
135	Candy Hard	Greedy Python3	☑️ 找规律 Trick
136	Single Number Easy	HashTable BitManipulation Python3	字典应用 Awesome XOR!
137	Single Number II Medium	HashTable BitManipulation Python3	hash 数学 Awesome XOR!
138	Copy List with Random Pointer Medium	LinkedList Python3	Two Pass HashMap
139	Word Break Medium	DynamicProgramming Python3	DP规律
140	Word Break II Hard	DynamicProgramming Python3	👍✅ DFS 记忆DP
141	Linked List Cycle Easy	LinkedList Python3	快慢指针
142	Linked List Cycle II Medium	LinkedList Python3	龟兔赛跑 快慢指针法
143	Reorder List Medium	LinkedList Python3	找中点反转归并
144	Binary Tree Preorder Traversal Medium	BinaryTree Python3	递归法 栈迭代法
145	Binary Tree Postorder Traversal Hard	BinaryTree Python3	递归法 栈迭代法
146	LRU Cache Medium	LinkedList Python3	👍 哈希表+链表
147	Insertion Sort List Medium	LinkedList Python3
148	Sort List Medium	LinkedList Python3	👍 通过要求Strict
149	Max Points on a Line Hard	HashTable Math Python3	👍☑️ 哈希表枚举
150	Evaluate Reverse Polish Notation Medium	Stack Python3	栈模拟
151	Reverse Words in a String Medium	String Python3	One Line Solution 数组翻转拼接
152	Maximum Product Subarray Medium	Array Counter Python3	👍 递归
153	Find Minimum in Rotated Sorted Array Medium	BinarySearch Python3	朴素 折半
154	Find Minimum in Rotated Sorted Array II Hard	Array BinarySearch Python3	👍 折半
155	Min Stack Easy	Stack PriorityQueue Python3
156	Binary Tree Upside Down Medium	BinaryTree Python3	🔒 栈模拟
157	Read N Characters Given Read4 Easy	String Python3	🔒 理解题意
158	Read N Characters Given Read4 II - Call multiple times Hard	String Python3	🔒 模拟
159	Longest Substring with At Most Two Distinct Characters Hard	HashTable TwoPointers String maxSlidingWindow Python3	👍🔒 滑动窗口 二刷滑动窗口
160	Intersection of Two Linked Lists Easy	LinkedList Python3	双指针
161	One Edit Distance Medium	String Python3	🔒 数组扫描
162	Find Peak Element Medium	BinarySearch Python3	单调区间的变换点
163	Missing Ranges Medium	Array Python3	👍lock: 模拟数组扫描
164	Maximum Gap Hard	Sort Python3	👍✅ 快速排序 基数排序 桶排序 鸽笼原理
165	Compare Version Numbers Medium	String Python3	字符串操作
166	Fraction to Recurring Decimal Medium	String HashTable Math Python3	循环节的处理
167	Two Sum II - Input array is sorted Easy	Math Sum Python3	哈希表 双指针
168	Excel Sheet Column Title Easy	Math Python3	模拟
169	Majority Element Easy	Array Python3
170	Two Sum III - Data structure design Easy	Design HashTable Python3	🔒 哈希简单应用
171	Excel Sheet Column Number Easy	Math Python3	遍历模拟
172	Factorial Trailing Zeroes Easy	Math BitManipulation Python3	👍 质数分解
173	Binary Search Tree Iterator Easy	BinarySearchTree Python3	栈模拟中序遍历
174	Dungeon Game Hard	BinarySearch DynamicProgramming Python3	👍🔝☑️ DP逆向推导
179	Largest Number Medium	Sort Python3	👍 自定义排序 Trick
186	Reverse Words in a String II Medium	String Python3	🔒 模拟数组扫描
187	Repeated DNA Sequences Medium	String HashTable BitManipulation Python3	哈希
188	Best Time to Buy and Sell Stock IV Hard	DynamicProgramming Python3	👍✅ DP法1 DP法2优化
189	Rotate Array Easy	Array Python3	👍✅🔝 模拟 翻转数组
190	Reverse Bits Easy	BitManipulation Python3	位运算模拟
191	Number of 1 Bits Easy	BitManipulation Python3	循环计数 位运算优化
198	House Robber Easy	DynamicProgramming Python3	DP与空间优化
199	Binary Tree Right Side View Medium	BinaryTree DFS BFS Python3	层序遍历模拟
200	Number of Islands Medium	DFS BFS UnionFind Python3	👍 BFS 置0数1 Google
201	Bitwise AND of Numbers Range Medium	BitManipulation Python3	找规律 位运算
202	Happy Number Easy	Math HashTable Python3	👍 字典模拟 龟兔赛跑
203	Remove Linked List Elements Easy	LinkedList Python3	模拟 头部节点的处理
204	Count Primes Easy	Math HashTable Python3	👍 筛法求素数
205	Isomorphic Strings Easy	String HashTable Python3	👍 哈希表映射
206	Reverse Linked List Easy	LinkedList Python3	逆序操作
207	Course Schedule Medium	TopologicalSort Python3	有向图中环是否存在
208	Implement Trie (Prefix Tree) Medium	Trie Python3	字典树 单词查找树
209	Minimum Size Subarray Sum Medium	Array TwoPointers BinarySearch Python3	双指针 滑动窗口
210	Course Schedule II Medium	DFS BFS TopologicalSort Python3	经典拓扑排序
211	Add and Search Word - Data structure design Medium	BackTracking Design Trie Python3	字典模拟 Trie(TODO)
212	Word Search II Hard	String BackTracking Trie Python3	👍✅ 递归回溯 Trie优化
213	House Robber II Medium	DynamicProgramming Python3	Rob First Or Not
214	Shortest Palindrome Hard	String Python3	👍✅ 最长前缀匹配 KMP优化
215	Kth Largest Element in an Array Medium	Stack PriorityQueue Python3	偷懒法 交换快排 最大堆 优先级队列 填坑快排 堆排
216	Combination Sum III Medium	BackTracking Python3	DFS
217	Contains Duplicate Easy	Array HashTable Python3	水题
218	The Skyline Problem Hard	Array DivideAndConquer Heap BinaryIndexedTree SegmentTree LineSweep Python3	👍✅ 思路转化 优先级队列 heapq
219	Contains Duplicate II Easy	Array HashTable Python3	哈希模拟
220	Contains Duplicate III Medium	Array Sort OrderedMap Python3	👍 滑动窗口 数学推导
221	Maximal Square Medium	DynamicProgramming Python3	👍 DP
222	Count Complete Tree Nodes Medium	BinarySearch BinaryTree Python3	👍☑️ BS in BS
223	Rectangle Area Medium	Math Python3	计算几何
224	Basic Calculator Hard	BackTracking Python3	值栈与符号栈
225	Implement Stack using Queues Easy	Stack Design Python3	双队实现栈
226	Invert Binary Tree Easy	BinaryTree Python3	递归 迭代
227	Basic Calculator II Medium	BackTracking Python3	乘除特殊处理
228	Summary Ranges Medium	Array Python3	模拟 线性扫描
229	Majority Element II Medium	Array Python3	👍 摩尔投票算法
230	Kth Smallest Element in a BST  Medium	BinarySearchTree   Python3	👍 递归 栈迭代
231	Power of Two Easy	Math BitManipulation Python3	基本数学 位运算
232	Implement Queue using Stacks Easy	Stack PriorityQueue Python3	双栈实现队列
234	Palindrome Linked List Easy	LinkedList TwoPointer Python3	双指针
235	Lowest Common Ancestor of a Binary Search Tree Easy	BinarySearchTree Python3	利用BST性质
236	Lowest Common Ancestor of a Binary Tree Medium	BinaryTree Python3	递归
237	Delete Node in a Linked List Easy	LinkedList Python3	取巧
238	Product of Array Except Self Medium	Array Math Python3	👍 前缀后缀积
239	Sliding Window Maximum Hard	Heap Sliding Window Python3	👍✅ 单调栈
240	Search a 2D Matrix II Medium	BinarySearch DivideAndConquer Python3	👍✅ 单调性扫描
241	Different Ways to Add Parentheses Medium	String Python3	递归分治
242	Valid Anagram Easy	String Python3	哈希表
243	Shortest Word Distance Easy	Array Python3	🔒 模拟数组扫描 模拟优化
244	Shortest Word Distance II Medium	Design HashTable Python3	🔒 模拟数组扫描 后处理优化
245	Shortest Word Distance III Medium	Array Python3	🔒 模拟数组扫描 后处理优化 特殊条件处理
246	Strobogrammatic Number Easy	Math HashTable Python3	🔒 双指针 Hash优化
247	Strobogrammatic Number II Medium	Math Recursion Python3	👍🔒 递归解法 迭代解法
248	Strobogrammatic Number III Hard	Math Recursion Python3	🔒 递归解法 边界处理
249	Group Shifted Strings Medium	String HashTable Python3	👍✅🔒 HashMap巧妙思路
250	Count Univalue Subtrees Medium	BinaryTree Recursion Python3	👍✅🔒 自底向上递归
251	Flatten 2D Vector Medium	Design Python3	🔒 展成一维存储 行列双变量控制
252	Meeting Rooms Easy	Sort Python3	🔒 蛮力(TLE) 排序检查
253	Meeting Rooms II Medium	Sort Greedy Heap Python3	👍☑️🔒 最小堆
254	Factor Combinations Medium	BackTracking Python3	🔒 自小到大 递归
255	Verify Preorder Sequence in Binary Search Tree Medium	BinarySearchTree Stack Python3	👍🔒 出入栈条件 空间优化
256	Paint House Easy	Array DynamicProgramming Python3	👍🔒 DP思路 更直观DP
257	Binary Tree Paths Easy	BinaryTree DFS Python3	DFS 递归 迭代
258	Add Digits Easy	Math Python3	模拟 公式法
259	3Sum Smaller Medium	Array TwoPointers Python3	🔒 暴力枚举 双指针
260	Single Number III Medium	HashTable BitManipulation Python3	Awesome XOR!
261	Graph Valid Tree Medium	Graph UnionFind DFS BFS Python3	👍🔒 并查集
263	Ugly Number Medium	Math Python3	模拟
264	Ugly Number II Medium	Math Python3	👍✅ 三指针法
265	Paint House II Hard	DynamicProgramming Python3	👍🔝🔒 DP必刷
266	Palindrome Permutation Easy	String HashTable Python3	🔒 Set应用
267	Palindrome Permutation II Medium	String BackTracking Python3	👍😍✅🔒 回文串的生成思路 重复回文子串的处理
268	Missing Number Easy	HashTable BitManipulation Python3	数学方法 位运算方法
269	Alien Dictionary Hard	Graph TopologicalSort Python3	👍😍✅☑️🔒 思路 出入度管理 图的构建 拓扑遍历 必刷好题
270	Closest Binary Search Tree Value Easy	BinarySearch BinarySearchTree Python3	🔒 中序查找 二分查找
271	Encode and Decode Strings Medium	String Design Python3	🙄🔒 无聊字符串操作
272	Closest Binary Search Tree Value II Hard	BinarySearchTree Stack Python3	👍✅🔒 中序遍历更新结果
273	Integer to English Words Hard	String Python3	👍✅ 模拟
274	H-Index Medium	HashTable Sort Python3	模拟
275	H-Index II Medium	BinarySearch Python3	构造二段性
276	Paint Fence Easy	DynamicProgramming Python3	👍🔒 数学分析方法
277	Find the Celebrity Medium	Array Python3	👍✅🔒 指定API 暴力法 验证法
278	First Bad Version Easy	BinarySearch Python3	线性查找超时 折半查找
279	Perfect Squares Medium	Math DynamicProgramming BFS Python3	👍✅ DP BFS
280	Wiggle Sort Medium	Array Sort Python3	🔒 排序交换 遍历规律
281	Zigzag Iterator Medium	Design Python3	🔒 保存时处理 访问时处理
282	Expression Add Operators Hard	BackTracking Python3	👍✅ DFS+表达式求值 求值时的特殊处理
283	Move Zeroes Easy	TwoPointers Python3	遍历并重新赋值
284	Peeking Iterator Medium	Design Python3	iterator小改动
285	Inorder Successor in BST Medium	BinarySearchTree Python3	👍☑️🔒 迭代中序遍历
286	Walls and Gates  Medium	Array BFS  Python3	:+1::lock: BFS DFS
287	Find the Duplicate Number Medium	BinarySearch Python3	Counter计数 set去重 👍构造两段性
288	Unique Word Abbreviation Medium	Design HashTable Python3	👍🔒 Set与Dict灵活应用
289	Game of Life Medium	Array Python3	模拟 Trick
290	Word Pattern Easy	String HashTable Python3	👍 205题扩展 哈希表映射
291	Word Pattern II  Hard	String BackTracking Python3	:+1::white_check_mark::lock: 递归回溯
292	Nim Game Easy	Brainteaser Python3	水题唬人
293	Flip Game Medium	String BackTracking Minimax Python3	🔒 遍历翻转
294	Flip Game II Easy	String Python3	🔒 遍历递归判断
295	Find Median from Data Stream Hard	Design Heap Python3	👍✅😍 双堆
296	Best Meeting Point Hard	Math Sort Python3	👍🔒 排序隐性考察
297	Serialize and Deserialize Binary Tree Hard	BinaryTree Python3	👍 递归DFS
298	Binary Tree Longest Consecutive Sequence Medium	BinaryTree Python3	👍🔒 中序遍历 栈的应用
299	Bulls and Cows Easy	String HashTable Python3	👍🔒 哈希表灵活应用
300	Longest Increasing Subsequence Medium	DynamicProgramming Python3	DP与优化
301	Remove Invalid Parentheses Hard	BackTracking Python3	👍 DFS+括号序列
302	Smallest Rectangle Enclosing Black Pixels  Hard	Array BinarySearch  Python3	:+1::white_check_mark::lock: 原始线性搜索 二分搜索
303	Range Sum Query - Immutable  Easy	Array DynamicProgramming  Python3	前缀和数组
304	Range Sum Query 2D - Immutable  Medium	Array DynamicProgramming  Python3	:+1::white_check_mark: 二维前缀和数组
305	Number of Islands II  Hard	UnionFind  Python3	:+1::white_check_mark::lock: BFS UFS 二维转化一维
306	Additive Number  Medium	BackTracking  Python3	递归模拟 长度限制
307	Range Sum Query - Mutable Medium	BinaryIndexTree SegmentTree Python3	树状数组
308	Range Sum Query 2D - Mutable Hard	BinaryIndexTree SegmentTree Python3	👍✅🔒 行之和 前缀数组
309	Best Time to Buy and Sell Stock with Cooldown Medium	DynamicProgramming Python3	👍✅ 带约束DP
310	Minimum Height Trees Medium	BFS Graph Python3
311	Sparse Matrix Multiplication Medium	Array HashTable Python3	🔒 非0才相乘
312	Burst Balloons Hard	DynamicProgramming Python3	👍 FunnyDPQuestion
313	Super Ugly Number Medium	Math Heap Python3	👍 模拟 264扩展
314	Binary Tree Vertical Order Traversal Medium	BinaryTree HashTable Python3	👍🔒 层序遍历 横向排序
315	Count of Smaller Numbers After Self Hard	BinarySearch DivideAndConquer Sort BinaryIndexTree SegmentTree Python3
317	Shortest Distance from All Buildings Hard	Array BFS DFS Python3	👍✅🔒 BFS 多变量更新
319	Bulb Switcher Medium	Math BrainTeaser Python3	👍 数论
320	Generalized Abbreviation Medium	String BackTracking BitManipulation Python3	👍✅🔒 递归回溯 位运算Trick
322	Coin Change Medium	DynamicProgramming Python3	DP完全背包
323	Number of Connected Components in an Undirected Graph Medium	UnionFind Graph DFS BFS Python3	👍✅🔒 简单UFS 路径压缩 Rank合并
324	Wiggle Sort II Medium	Sort Python3	☑️排序规律划分 Follow Up(TODO)
325	Maximum Size Subarray Sum Equals k Medium	Array HashTable Python3	👍✅🔒 前缀和数组 保存出现最早位置 Trick
326	Power of Three Easy	Math BitManipulation Python3	基本数学 数论 log逆运算
328	Odd Even Linked List Medium	LinkedList Python3	👍✅ 指针拆分 Dummy Node
329	Longest Increasing Path in a Matrix Hard	Memorization Python3	DFS
331	Verify Preorder Serialization of a Binary Tree Medium	BinaryTree Python3	入度出度之差 砍叶子:fallen_leaf:
332	Reconstruct Itinerary Medium	Graph DFS Python3	👍🔝☑️ 贪心回溯 Hierholzer's Algorithm
333	Largest BST Subtree Medium	BinaryTree BinarySearchTree Python3	👍✅🔒 自底向上
336	Palindrome Pairs Hard	HashTable String Trie Python3	找规律 哈希
337	House Robber III Medium	BinaryTree DynamicProgramming Python3	👍✅ 树形DP
338	Counting Bits Medium	DynamicProgramming BitManipulation Python3	👍✅ DP Most Significant Least Significant
339	Nested List Weight Sum Easy	Array DFS Python3	👍🔒 DFS
340	Longest Substring with At Most K Distinct Characters Hard	String HashTable SlidingWindow Python3	👍🔒 滑动窗口 159题扩展
341	Flatten Nested List Iterator Medium	Stack Design Python3	👍 队列迭代 DFS预处理
342	Power of Four Easy	Math BitManipulation Python3	基本数学 位运算 数论
343	Integer Break Medium	Math DynamicProgramming Python3	👍 DP 数学
344	Reverse String Easy	String TwoPointers Python3	两端双指针
345	Reverse Vowels of a String Easy	String TwoPointers Python3	两端过滤双指针 记录逆序替换
346	Moving Average from Data Stream Easy	Design Queue Python3	🔒 队列 数满则溢
347	Top K Frequent Elements Medium	Stack PriorityQueue Python3	Counter计数 桶排序
348	Design Tic-Tac-Toe Medium	Design Python3	👍✅🔒 直观Grid 伴随统计
349	Intersection of Two Arrays Easy	Array HashTable TwoPointers BinarySearch Sort Python3	暴力统计 字典求解
350	Intersection of Two Arrays II Easy	Array HashTable TwoPointers BinarySearch Sort Python3	字典哈希 Google
351	Android Unlock Patterns Medium	Array BackTracking DynamicProgramming Python3	👍☑️🔒 递归回溯 对称性
352	Data Stream as Disjoint Intervals Hard	UnionFind BinarySearch OrderedMap Python3	👍☑️ 并查集
353	Design Snake Game Hard	Design Python3	👍🔒 模拟 Deque应用
354	Russian Doll Envelopes Hard	DynamicProgramming BinarySearch Python3	👍☑️ 常规DP DP优化
355	Design Twitter Easy	Design HashTable Heap Python3	👍☑️
356	Line Reflection Medium	Array Math HashTable Python3	👍🔒 找中心 判对称
358	Rearrange String k Distance Apart Hard	String Heap Greedy Python3	👍✅🔒 贪心 最高频率分桶
359	Logger Rate Limiter Easy	Design HashTable Python3	🔒 哈希表简单应用
360	Sort Transformed Array Medium	Array Math TwoPointers Sort Python3	👍🔒 蛮力 双指针
361	Bomb Enemy Medium	Array DynamicProgramming Python3	👍✅🔒 BruteForce DP
362	Design Hit Counter Medium	Design Python3	👍🔒 Deque应用 空间换时间
363	Max Sum of Rectangle No Larger Than K Hard	BinarySearch DynamicProgramming Queue Python3	😢👍☑️ 枚举 前缀和优化 Kadane算法 二分优化
364	Nested List Weight Sum II Medium	Array DFS Python3	👍✅🔒 统计层序和再逆序求和
366	Find Leaves of Binary Tree Medium	BinaryTree DFS Python3	👍🔒 递归后序 深度扩展
367	Valid Perfect Square Easy	BinarySearch Math Python3
368	Largest Divisible Subset Medium	Math DynamicProgramming Python3	规律DP
369	Plus One Linked List Medium	LinkedList Python3	👍✅🔒 两次翻转 Trick
370	Range Addition Medium	Array Math Python3	👍✅🔒 RangeCaching Trick
371	Sum of Two Integers Easy	BitManipulation Python3	👍🔝 位运算
374	Guess Number Higher or Lower Easy	BinarySearch Python3	折半查找
375	Guess Number Higher or Lower II Medium	DynamicProgramming Python3	DP+MiniMax
376	Wiggle Subsequence Medium	DynamicProgramming Greedy Python3
378	Kth Smallest Element in a Sorted Matrix Medium	Matrix Python3	Counter或桶排序
379	Design Phone Directory Medium	Design LinkedList Python3	🔒
380	Insert Delete GetRandom O(1) Medium	Design Array HashTable Python3	👍 dict+list Trick
382	Linked List Random Node Medium	ReservoirSampling Python3	Two Pass 蓄水池采样
383	Ransom Note Easy	String Python3	模拟 哈希表
384	Shuffle an Array Medium	Random Python3	random互换
387	First Unique Character in a String Easy	String HashTable Python3	哈希模拟
389	Find the Difference Easy	HashTable BitManipulation Python3
392	Is Subsequence Easy	String HashTable Greedy BinarySearch Python3	👍🔝 哈希速度优化 二分
394	Decode String Medium	Stack DFS Python3	👍✅ 递归 栈
399	Evaluate Division Medium	UnionFind Graph Python3	哈希模拟 并查集
401	Binary Watch Easy	BackTracking BitManipulation Python3	遍历count验证
402	Remove K Digits Medium	Greedy Python3	栈的应用
405	Convert a Number to Hexadecimal Easy	BitManipulation Python3	特殊处理负数
406	Queue Reconstruction by Height Medium	Greedy Python3	👍 贪心性质发现 模拟
407	Trapping Rain Water II Hard	Heap BFS Python3	👍✅ BFS
408	Valid Word Abbreviation Easy	String Python3	🔒 双指针 字符数字分别处理
409	Longest Palindrome Easy	HashTable Python3	奇偶分别考虑
410	Split Array Largest Sum Hard	BinarySearch DynamicProgramming Python3	👍 二分贪心 DP
411	Minimum Unique Word Abbreviation  Hard	BackTracking BitManipulation  Python3	👍🔝☑️🔒 边缩写边检查 Abbreviation综合考察
412	Fizz Buzz Easy	String Python3	简单明了
414	Third Maximum Number Easy	Array Sort Python3	三变量更新
415	Add Strings Easy	String Python3	模拟
416	Partition Equal Subset Sum Medium	DynamicProgramming Python3	包装01背包问题 空间优化
418	Sentence Screen Fitting Medium	Array DynamicProgramming Python3	👍✅🔒 建表查表 冲突回滚
421	Maximum XOR of Two Numbers in an Array Medium	BitManipulation Trie Python3	👍🔝😍 位前缀哈希 Trie树
422	Valid Word Square Easy	Array String Math Python3	🔒 越界判断 对应比较
425	Word Squares  Hard	String BackTracking Trie  Python3	:+1::top::white_check_mark::lock: 前缀字典 前缀树经典应用
426	Convert Binary Search Tree to Sorted Doubly Linked List Medium	BinarySearchTree LinkedList DivideAndConquer Python3	👍🔒 中序递归 InPlace
428	Serialize and Deserialize N-ary Tree  Hard	Tree String  Python3	:+1::top::ballot_box_with_check::lock: 先序递归遍历
429	N-ary Tree Level Order Traversal  Medium	Tree BFS  Python3	BFS extend
430	Flatten a Multilevel Doubly Linked List  Medium	LinkedList DFS  Python3	👍 迭代DFS
431	Encode N-ary Tree to Binary Tree Hard	BinaryTree Python3	👍🔒 N-ary to Binary
438	Find All Anagrams in a String  Medium	HashTable  Python3	哈希表 滑动窗口
439	Ternary Expression Parser  Medium	String Stack DFS  Python3	:+1::lock: 自右向左处理
441	Arranging Coins  Easy	BinarySearch Math  Python3	:+1::ballot_box_with_check: 模拟 数学推导 二分查找
444	Sequence Reconstruction  Medium	String Graph TopologicalSort  Python3	:+1::white_check_mark::lock: 相邻顺序对应 记录已出现 枚举判断
447	Number of Boomerangs  Easy	HashTable Math  Python3	:+1: 距离相等点+1 组合数+2
451	Sort Characters By Frequency Medium	HashTable Heap Python3	哈希+heapq
452	Minimum Number of Arrows to Burst Balloons Medium	Greedy Python3	👍 排序贪心
454	4Sum II Easy	Array HashTable BinarySearch Python3	👍✅ 哈希转化
455	Assign Cookies Easy	Greedy Python3	贪心
456	132 Pattern Medium(Hard)	Array Stack Python3	👍✅ 单调栈扩展
458	Poor Pigs Hard	Math Brainteaser Python3	👍 数学分析 找规律
461	Hamming Distance Easy	BitManipulation Python3	Brian Kernighan's Algorithm
462	Minimum Moves to Equal Array Elements II Medium	Math Python3	分奇偶找中值
463	Island Perimeter Easy	HashTable Python3	模拟 memo思想
464	Can I Win Medium	DynamicProgramming Minimax Python3	👍🔝 Minimax博弈 记忆化递归
465	Optimal Account Balancing Hard	Array Math Python3	👍🔝✅🔒 哈希表 集合 DFS 综合应用
468	Validate IP Address Medium	String Python3	模拟 Regex
469	Convex Polygon Medium	Array Math Python3	👍✅🔒 凸多边形性质 叉乘应用
470	Implement Rand10() Using Rand7() Medium	RejectionSampling Python3
471	Encode String with Shortest Length Hard	String>br>DynamicProgramming Python3	👍🔝🔒 二维DP
473	Matchsticks to Square Medium	BackTracking Python3	DFS 长者为先
475	Heaters Easy	Array BinarySearch Python3	贪心法 二分法
476	Number Complement Easy	BitManipulation Python3	模拟 位运算规律
477	Total Hamming Distance Medium	BitManipulation Python3	按位统计
481	Magical String Medium	String Python3	👍规律模拟
482	License Key Formatting Easy	String Python3	字符串基础操作 模拟 Google
484	Find Permutation Medium	Greedy Python3	👍🔒 贪心栈
485	Max Consecutive Ones Easy	Array Python3	水题
486	Predict the Winner Medium	DynamicProgramming MiniMax Python3	DP
487	Max Consecutive Ones II Medium	TwoPointers SlidingWindow Python3	🔒 分两段 滑动窗口 流式记录
489	Robot Room Cleaner Medium	DFS BackTracking Python3	🔒 DFS回溯
490	The Maze Medium	Arrays DFS BFS Python3	👍✅🔒 DFS
496	Next Greater Element I Easy	Stack Python3	遍历查找 单调栈与hashmap
499	The Maze III Hard	Array DFS BFS Python3	👍✅🔒 DFS
500	Keyboard Row Easy	Math HashTable Python3	字符串in操作 集合元素求交集
501	Find Mode in Binary Search Tree Easy	BinarySearchTree Python3	中序遍历 遍历查相邻
503	Next Greater Element II Medium	Stack Python3	遍历查找(TLE) 单调栈
504	Base 7 Easy	Math Python3	Flag and Mod
505	The Maze II Medium	Array DFS BFS Python3	👍✅🔒 DFS
506	Relative Ranks Easy	Array Sort HashTable Python3	排序查表
507	Perfect Number Easy	Math Python3	👍 暴力枚举 枚举优化
509	Fibonacci Number Easy	Array Math Python3	👍🔝 原始递归 尾递归 DP循环 空间优化
510	Inorder Successor in BST II Medium	BinarySearchTree Python3	👍🔒 分情况讨论 右分支有无
513	Find Bottom Left Tree Value Medium	BinaryTree DFS BFS Python3	模拟层序遍历
518	Coin Change 2 Medium	DynamicProgramming Python3	👍 二维DP 一维DP
520	Detect Capital Easy	String Python3	字符串基本函数
521	Longest Uncommon Subsequence II Easy	String Python3	BrainTeaser
525	Contiguous Array Medium	Array HashTable Python3	👍 前缀和 + 哈希表转化
526	Beautiful Arrangement Medium	BackTracking Python3	☑️ 回溯
527	Word Abbreviation Hard	String Sort Python3	👍✅🔒 规则分桶 LCP求解 消除冲突
528	Random Pick with Weight Medium	Design BinarySearch Random Python3	问题建模
530	Minimum Absolute Difference in BST Easy	BinaryTree Python3	中序遍历 有序数组中找最小差值
531	Lonely Pixel I Medium	Array DFS Python3	👍🔒 两次遍历
532	K-diff Pairs in an Array Easy	Array TwoPointers Python3	统计数频 特判k为0
533	Lonely Pixel II Medium	Array DFS Python3	🔒
540	Single Element in a Sorted Array Medium	Array Python3	位运算 折半查找
541	Reverse String II Easy	String TwoPointers Python3	分段处理 两端双指针
542	01 Matrix Medium	DFS BFS Python3	👍✅ 蛮力(TLE) BFS DP
543	Diameter of Binary Tree Easy	BinaryTree Python3	DFS
544	Output Contest Matches Medium	Array Half-Fold Python3	🔒 折半两端匹配
545	Boundary of Binary Tree Medium	BinaryTree Python3	👍☑️🔒 分部处理 左右逆序
547	Friend Circles Medium	UnionFind DFS Python3	👍 并查集入门题
548	Split Array with Equal Sum Medium	Array Math Python3	👍🔝✅🔒 贪心 前缀和 HashTable优化 中点分两段
551	Student Attendance Record I Easy	String Python3	模拟
554	Brick Wall Medium	Array HashTable Python3	👍✅ 贪心+哈希表
555	Split Concatenated Strings Medium	String Python3	枚举 高位优先优化
556	Next Greater Element III Medium	String Math Python3	👍✅ 找规律
560	Subarray Sum Equals K Medium	Array HashTable Python3	前缀和 + 哈希表
567	Permutation in String Medium	TwoPointers SlidingWindow Python3	滑动窗口
572	Subtree of Another Tree Easy	BinaryTree Python3	递归先序 模拟比较
582	Kill Process Medium	BinaryTree Queue Python3	👍🔒 字典记录父子关系 队列实现逐层杀死
583	Delete Operation for Two Strings Medium	String Python3	👍✅ 双DP LCS Edit Distance
588	Design In-Memory File System Hard	Design Python3	👍🔒 分别处理文件与文件夹
604	Design Compressed String Iterator Easy	Design String Python3	✅🔒 Demand-Computation
611	Image Smoother Easy	Array Python3	依题意操作
616	Add Bold Tag in String Medium	String Python3	🔒 Bold Flag 与758题雷同
624	Maximum Distance in Arrays Easy	Array HashTable Python3	🔒
625	Minimum Factorization Medium	Math Recursion Python3	🔒 贪心因式分解
634	Find the Derangement of An Array  Medium	Math  Python3	:lock: DP 组合错排问题 空间优化
635	Design Log Storage System Medium	String Design Python3	👍🔒 提取比较
643	Maximum Average Subarray I Easy	Array Math Python3	遍历更新
644	Maximum Average Subarray II Hard	Array Math BinarySearch Python3	👍🔝✅🔒 蛮力TLE 折半查找 滑动窗口
650	2 Keys Keyboard Medium	DynamicProgramming Python3	👍 DP 递归 数学
652	Find Duplicate Subtrees Medium	BinaryTree Python3	👍DFS 哈希 关注局部
653	Two Sum IV - Input is a BST Easy	BinarySearchTree Python3	中序遍历 已排序数组两数之和为target
657	Robot Return to Origin Easy	String Python3	抵消count 模拟
658	Find K Closest Elements Medium	BinarySearch Python3	👍✅ 排序 双指针 二分查找
662	Maximum Width of Binary Tree Medium	BinaryTree Python3	👍✊ BFS DFS
664	Strange Printer Hard	DynamicProgramming DFS Python3	👍✅ DP进阶题目
681	Next Closest Time Hard	String Python3	🔒 模拟 Google
684	Redundant Connection Medium	Tree UnionFind Graph Python3	👍 并查集
687	Longest Univalue Path Easy	Recursion Python3	DFS递归
692	Top K Frequent Words Medium	Array HashTable Heap Trie Python3	👍✅ 优先队列改造题
695	Max Area of Island Medium	Array DFS BFS Python3	递归DFS 队列BFS
697	Degree of an Array Easy	Array Python3	统计查表
700	Search in a Binary Search Tree Easy	BinarySearchTree Python3	递归 迭代
703	Kth Largest Element in a Stream Easy	Heap Python3	维护k个元素的最小堆
704	Binary Search Easy	BinarySearch Python3	依题意
705	Design HashSet Easy	HashTable Design Python3	数组模拟
706	Design HashMap Easy	HashTable Design Python3	数组模拟
716	Max Stack Easy	Stack Design Python3	👍🔒 双栈模拟
728	Self Dividing Numbers Easy	Math Python3	模拟
729	My Calendar I Medium	Array Python3	蛮力 Need Imporve
731	My Calendar II Medium	OrderedMap Python3	👍 729再重叠
733	Flood Fill Easy	DFS BFS Python3	队列BFS 递归DFS
734	Sentence Similarity Easy	String HashTable Python3	🔒 Tuple与Set
737	Sentence Similarity II Medium	String DFS UnionFind Python3	👍🔒 并查集
743	Network Delay Time Medium	Heap DFS BFS Graph Python3	☑️ Dijkstra算法 Bellman-Ford算法
746	Min Cost Climbing Stairs Easy	Array DynamicProgramming Python3	👍 70题扩展 两种DP
751	IP to CIDR Easy	Greedy BitManipulation Python3	👍🔒 贪心最大块 位运算查找
755	Pour Water Medium	Array Simulation Python3	🔒 模拟流动 左边优先
756	Pyramid Transition Matrix Medium	BitManipulation DFS Python3	👍 模拟 DFS&BFS
758	Bold Words in String Easy	String Python3	👍🔒 Bold Flag
762	Prime Number of Set Bits in Binary Representation Easy	BitManipulation Python3	👍 枚举 位运算技巧
771	Jewels and Stones Easy	String Python3	水题
777	Swap Adjacent in LR String Medium	Brainteaser Python3	👍✅ 找规律 Funny
784	Letter Case Permutation Easy	BackTracking BitManipulation Python3	DFS
785	Is Graph Bipartite? Medium	Graph DFS BFS Python3	DFS模拟
787	Cheapest Flights Within K Stops Medium	DFS BFS Python3	👍☑️ 数值引用传递
800	Similar RGB Color Easy	String Math Python3	🔒 蛮力求解 数学分析
809	Expressive Words Medium	String Python3	模拟 分段核对
829	Consecutive Numbers Sum Hard	Math Python3	👍 数学分析 等差数列求和
840	Magic Squares In Grid Easy	Array Python3	枚举检查
843	Guess the Word Hard	Minimax Python3	👍 Google 交互问题
846	Hand of Straights Easy	Heap Python3	Counter应用
849	Maximize Distance to Closest Person Easy	Array Python3	滑动窗口 两侧特殊处理 Google
852	Peak Index in a Mountain Array Easy	Array BinarySearch Python3	线性 折半
857	Minimum Cost to Hire K Workers Hard	Heap Python3	👍✅🔝 贪心最大堆
860	Lemonade Change Easy	Greedy Python3	贪心
883	Projection Area of 3D Shapes Medium	Array Math Python3	规律计算
886	Possible Bipartition Medium	DFS Python3	建图+785
891	Sum of Subsequence Widths Hard	Array Math Python3	👍 数学规律
892	Surface Area of 3D Shapes Easy	Math Geometry Python3	找规律问题
901	Online Stock Span Medium	Stack Python3	蛮力算法 栈记忆
904	Fruit Into Baskets Medium	TwoPointers Python3	滑动窗口 159题包装 Google
918	Maximum Sum Circular Subarray Medium(Hard)	Array Python3	👍✅ 前缀和单调队列 分情况讨论
929	Unique Email Addresses Easy	String Python3	哈希表 字符串处理 Google
930	Binary Subarrays With Sum Medium	HashTable TwoPointers Python3	👍☑️🔝 记录基本元素位置 前缀和+counts
933	Number of Recent Calls Easy	Queue Python3	二分查找 队列
957	Prison Cells After N Days Medium	HashTable Python3	大数模拟 必有循环
973	K Closest Points to Origin Medium	DivideAndConquer Heap Sort Python3	👍☑️ 调库 分治 最小堆
975	Odd Even Jump Hard	DynamicProgramming Stack OrderedMap Python3	👍☑️ 单调栈 记忆化递归 Google
986	Interval List Intersections Medium	TwoPointers Python3	✅ 双指针
989	Add to Array-Form of Integer Easy	Array Python3	逐位相加进位
993	Cousins in Binary Tree Easy	BinaryTree Python3	DFS或BFS预处理
997	Find the Town Judge Easy	Graph Python3	集合模拟 出入度
999	Available Captures for Rook Easy	Array Python3	暴力枚举
1002	Find Common Characters Easy	Array HashTable Python3	小根堆
1004	Max Consecutive Ones III Medium	TwoPointers SlidingWindow Python3	滑动窗口
1005	Maximize Sum Of Array After K Negations Easy	Greedy Python3	小根堆
1006	Clumsy Factorial Medium	Math Python3	直接计算 eval函数
1008	Construct Binary Search Tree from Preorder Traversal Medium	BinaryTree Python3	递归
1009	Complement of Base 10 Integer Easy	Math Python3	进制转化
1010	Pairs of Songs With Total Durations Divisible by 60 Easy	Math Array Python3	统计频次 组合计算
1011	Capacity To Ship Packages Within D Days Medium	Array BinarySearch Python3	二分 模拟
1013	Partition Array Into Three Parts With Equal Sum Easy	Array Python3	线性扫描
1014	Best Sightseeing Pair Medium	Array Python3	线性扫描
1015	Smallest Integer Divisible by K Medium	Math Python3	暴力枚举
1016	Binary String With Substrings Representing 1 To N Medium	String Python3	子串枚举
1021	Remove Outermost Parentheses Easy	String Stack Python3	栈
1022	Sum of Root To Leaf Binary Numbers Easy	BinaryTree Python3	👍 DFS
1023	Camelcase Matching Medium	String Trie Python3	直接查找 + 检查
1025	Divisor Game Easy	Math DynamicProgramming Python3	数学推导
1026	Maximum Difference Between Node and Ancestor Medium	BinaryTree DFS Python3	DFS
1029	Two City Scheduling Easy	Greedy Python3	排序贪心
1035	Uncrossed Lines Medium	Array Python3	DP基础题
1044	Longest Duplicate Substring Hard	HashTable BinarySearch Python3	☑️ Rabin-Karp 1062扩展
1056	Confusing Number Easy	Math Python3	🔒 记录翻转对 注意拼接顺序
1062	Longest Repeating Substring Medium	String BinarySearch Python3	☑️ Set Hash Rabin-Karp
1064	Fixed Point Easy	Array BinarySearch Python3	🔒 水题
1065	Index Pairs of a String Easy	String Trie Python3	🔒 查找排序
1085	Sum of Digits in the Minimum Number Easy	Array Python3	🔒 模拟
1086	High Five Easy	Array HashTable Sort Heap Python3	🔒 大根堆
1099	Two Sum Less Than K Easy	Array Python3	🔒 双指针
1103	Distribute Candies to People Easy	Math Python3	👍 模拟 数学推导
1118	Number of Days in a Month Easy	HashTable Python3	🔒 分闰平
1119	Remove Vowels from a String Easy	String Python3	🔒 字符串基本操作
1133	Largest Unique Number Easy	Array HashTable Python3	👍🔒 字典 调库 排序过滤
1134	Armstrong Number Easy	Math Python3	🔒 水题
1135	Connecting Cities With Minimum Cost Medium	UnionFind Graph Python3	最小生成树 Kruskal算法 Prim算法
1137	N-th Tribonacci Number Easy	Math Recursion Python3	👍✅🔒 DP 记忆递归 记忆DP
1140	Stone Game II  Medium	DynamicProgramming  Python3	☑️ DP
1143	Longest Common Subsequence  Medium	DynamicProgramming  Python3	二维DP
1150	Check If a Number Is Majority Element in a Sorted Array Easy	Array BinarySearch Python3	🔒 水题
1154	Day of the Year Easy	Math Python3	分段处理 特判闰年
1165	Single-Row Keyboard Easy	String Python3	🔒 记录下标 遍历统计
1169	Invalid Transactions Medium	Array String Python3	蛮力模拟 👍分组排序过滤
1175	Prime Arrangements Easy	Math Python3	👍✅🔝 暴力法求质数 欧拉筛法求质数
1176	Diet Plan Performance Easy	Array SlidingWindow Python3	🔒 滑动窗口
1180	Count Substrings with Only One Distinct Letter Easy	Math String Python3	🔒 组合数 找规律
1184	Distance Between Bus Stops Easy	Array Python3	模拟
1185	Day of the Week Easy	Array Python3	形参同名问题
1189	Maximum Number of Balloons Easy	HashTable String Python3	计数看瓶颈
1196	How Many Apples Can You Put into the Basket Easy	Array Greedy Python3	🔒 轻者优先
1197	Minimum Knight Moves Medium	DFS BFS Python3	🔒👍 普通BFS 对称优化BFS
1200	Minimum Absolute Difference Easy	Array Python3	🔒 相邻差最小
1207	Unique Number of Occurrences Easy	HashTable Python3	统计核对
1213	Intersection of Three Sorted Arrays Easy	Array HashTable TwoPointers Python3	🔒 Set交集 Counter计数 三指针
1215	Stepping Numbers Medium	BackTracking Python3	🔒🔝✅ 模拟 DFS BFS
1227	Airplane Seat Assignment Probability Medium	Math DynamicProgramming Brainteaser Python3	👍✅ DP推导 数学证明
1228	Missing Number In Arithmetic Progression Easy	Array Math Python3	🔒 找出差 逐个核查
1229	Meeting Scheduler Medium	Array LineSweep Python3	🔒 贪心双指针
1232	Check If It Is a Straight Line Easy	Array Math Geometry Python3	👍斜率公式转化
1236	Web Crawler Medium	HashTable DFS BFS Python3	👍🔒 DFS遍历 Set去重
1243	Array Transformation Easy	Array Python3	🔒 模拟
1244	Design A Leaderboard Medium	HashTable Sort Design Python3	🔒 基础
1245	Tree Diameter Medium	Tree DFS BFS Python3	😍🔒 建图 DFS
1247	Minimum Swaps to Make Strings Equal Medium	String Greedy Python3	找规律 贪心
1256	Encode Number Medium	Math BitManipulation Python3	🔒 找规律
1266	Minimum Time Visiting All Points Easy	Array Geometry Python3	画图规律遍历
1267	Count Servers that Communicate Medium	Array Graph Python3	枚举置位统计
1271	Hexspeak Easy	Math String Python3	🔒 模拟
1272	Remove Interval Medium	Math LineSweep Python3	🔒 模拟
1276	Number of Burgers with No Waste of Ingredients Medium	Math Greedy Python3	数学分析模拟
1277	Count Square Submatrices with All Ones Medium	Array DynamicProgramming Python3	🔝👍☑️ 动规好题
1281	Subtract the Product and Sum of Digits of an Integer Easy	Math Python3	模拟
1282	Group the People Given the Group Size They Belong To Medium	Greedy Python3	分组贪心
1287	Element Appearing More Than 25% In Sorted Array Easy	Array Python3	模拟
1290	Convert Binary Number in a Linked List to Integer Easy	LinkedList BitManipulation Python3	模拟
1296	Divide Array in Sets of K Consecutive Numbers Medium	Array Greedy Python3	排序 哈希模拟
1304	Find N Unique Integers Sum up to Zero Easy	Array Python3	模拟
1323	Maximum 69 Number Easy	Math Python3	基础字符串操作
1365	How Many Numbers Are Smaller Than the Current Number Easy	Array HashTable Python3	模拟 分桶前缀和
1389	Create Target Array in the Given Order Easy	Array Python3
1429	First Unique Number Medium	HashTable Design Python3	hash+deque

Database

#	Title	Difficulty	Solution	Notes
175	Combine Two Tables	Easy	SQL	left join
176	Second Highest Salary	Easy	SQL	IFNULL Count

Shell

#	Title	Difficulty	Solution	Notes
192	Word Frequency	Easy	Shell	👍
195	Tenth Line	Easy	Shell	sed awk head tail

Concurrency

#	Title	Difficulty	Solution	Notes
1114	Print in Order	Easy	Python3	acquire release
1279	Traffic Light Controlled Intersection	Easy	Python3	Lock BoundedSemaphore

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Contest

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Acknowledgments

• Grandyang
• fuxuemingzhu
• Hua Hua

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