SQL I

Day 1 Select


0595	大的国家	Easy	Database	417	56.09
1757	可回收且低脂的产品	Easy	Database	1237	34.20
0584	寻找用户推荐人	Easy	Database	779	43.48
0183	从不订购的客户	Easy	Database	712	33.67

Day 2 Select and Order


1873	计算特殊奖金	Easy	Database	1321	33.12
0627	变更性别	Easy	Database	400	51.04
0196	删除重复的电子邮箱	Easy	Database	593	94.17

Day 3 String Processing Functions


1667	修复表中的名字	Easy	Database	1196	61.40
1484	按日期分组销售产品	Easy	LeetCode_Curated_SQL_70, Database	899	40.76
1527	患某种疾病的患者	Easy	Database	708	48.23

Day 4 Union and Select


1965	丢失信息的雇员	Easy	Database	949	88.66
1795	每个产品在不同商店的价格	Easy	Database	1027	67.57
0608	树节点	Medium	LeetCode_Curated_SQL_70, Database	794	48.38
0176	第二高的薪水	Medium	Database	219	92.54

Day 5 Union


0175	组合两个表	Easy	Database	473	54.97
1581	进店却未进行过交易的顾客	Easy	Database	2771	54.68
1148	文章浏览 I	Easy	LeetCode_Curated_SQL_70, Database	806	54.41

Day 6 Union


0197	上升的温度	Easy	Database	394	94.15
0607	销售员	Easy	LeetCode_Curated_SQL_70, Database	2142	44.56

Day 7 Function


1141	查询近30天活跃用户数 I	Easy	LeetCode_Curated_SQL_70, Database	790	87.11
1693	每天的领导和合伙人	Easy	Database	1115	52.84
1729	求关注者的数量	Easy	Database	1228	38.04

Day 8 Function


0586	订单最多的客户	Easy	LeetCode_Curated_SQL_70, Database	768	44.85
0511	游戏玩法分析 I	Easy	LeetCode_Curated_SQL_70, Database	790	45.04
1890	2020年最后一次登录	Easy	Database	1280	43.62
1741	查找每个员工花费的总时间	Easy	Database	1101	51.40

Day 9 Control of Flow


1393	股票的资本损益	Medium	LeetCode_Curated_SQL_70, Database	990	47.36
1407	排名靠前的旅行者	Easy	LeetCode_Curated_SQL_70, Database	1394	98.43
1158	市场分析 I	Medium	Database	2470	44.76

Day 10 Where


0182	查找重复的电子邮箱	Easy	Database	396	68.40
1050	合作过至少三次的演员和导演	Easy	LeetCode_Curated_SQL_70, Database	629	81.02
1587	银行账户概要 II	Easy	Database	1582	52.96
1084	销售分析III	Easy	LeetCode_Curated_SQL_70, Database	1881	79.36

Level 1

Day 1 Prefix Sum


1480	一维数组的动态和	Easy	Array, Prefix_Sum	161	84.80
0724	寻找数组的中心下标	Easy	Array, Prefix_Sum	255	88.92

Day 2 String


0205	同构字符串	Easy	String, Hash_Table	278	79.96
0392	判断子序列	Easy	String, Dynamic_Programming, Two_Pointers	156	87.74

Day 3 Linked List


0021	合并两个有序链表	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(m+n)_Space_O(m+n)	157	92.24
0206	反转链表	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1)	279	45.78

Day 4 Linked List


0876	链表的中间结点	Easy	Two_Pointers, Linked_List	136	76.52
0142	环形链表 II	Medium	Top_100_Liked_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(N)_Space_O(1)	192	63.39

Day 5 Greedy


0121	买卖股票的最佳时机	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	609	94.06
0409	最长回文串	Easy	String, Hash_Table, Greedy	259	60.71

Day 6 Tree


0589	N 叉树的前序遍历	Easy	Depth_First_Search, Tree, Stack	233	84.02
0102	二叉树的层序遍历	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N)	198	95.14

Day 7 Binary Search


0704	二分查找	Easy	Top_100_Liked_Questions, Array, Binary_Search	261	77.91
0278	第一个错误的版本	Easy	Binary_Search, Interactive	349	76.86

Day 8 Binary Search Tree


0098	验证二叉搜索树	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(N)_Space_O(log(N))	190	61.62
0235	二叉搜索树的最近公共祖先	Medium	Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree	404	75.59

Day 9 Graph/BFS/DFS


0733	图像渲染	Easy	Array, Depth_First_Search, Breadth_First_Search, Matrix	230	97.76
0200	岛屿数量	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(MN)_Space_O(MN)	252	95.41

Day 10 Dynamic Programming


0509	斐波那契数	Easy	Dynamic_Programming, Math, Recursion, Memoization	139	82.72
0070	爬楼梯	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Memoization, Big_O_Time_O(n)_Space_O(n)	124	71.98

Day 11 Dynamic Programming


0746	使用最小花费爬楼梯	Easy	Array, Dynamic_Programming	171	96.76
0062	不同路径	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Combinatorics, Big_O_Time_O(mn)_Space_O(mn)	118	94.65

Day 12 Sliding Window/Two Pointer


0438	找到字符串中所有字母异位词	Medium	Top_100_Liked_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n+m)_Space_O(1)	561	54.68
0424	替换后的最长重复字符	Medium	String, Hash_Table, Sliding_Window	288	84.38

Day 13 Hashmap


0001	两数之和	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n)	202	91.18
0299	猜数字游戏	Medium	String, Hash_Table, Counting	254	84.82

Day 14 Stack


0844	比较含退格的字符串	Easy	String, Two_Pointers, Stack, Simulation	126	98.31
0394	字符串解码	Medium	Top_100_Liked_Questions, String, Stack, Recursion, Big_O_Time_O(n)_Space_O(n)	224	64.86

Day 15 Heap


1046	最后一块石头的重量	Easy	Array, Heap_Priority_Queue	123	100.00
0692	前K个高频单词	Medium	String, Hash_Table, Sorting, Heap_Priority_Queue, Counting, Trie, Bucket_Sort	239	81.10

Level 2

Day 1 Implementation/Simulation


0202	快乐数	Easy	Top_Interview_Questions, Hash_Table, Math, Two_Pointers	261	45.08
0054	螺旋矩阵	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Matrix, Simulation	132	95.12
1706	球会落何处	Medium	Array, Dynamic_Programming, Depth_First_Search, Matrix, Simulation	270	67.86

Day 2 String


0014	最长公共前缀	Easy	Top_100_Liked_Questions, Top_Interview_Questions, String	154	89.70
0043	字符串相乘	Medium	String, Math, Simulation	165	96.72

Day 3 Linked List


0019	删除链表的倒数第 N 个结点	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Two_Pointers, Linked_List, Big_O_Time_O(L)_Space_O(L)	144	96.28
0234	回文链表	Easy	Top_100_Liked_Questions, Two_Pointers, Stack, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(1)	641	79.53

Day 4 Linked List


0328	奇偶链表	Medium	Linked_List	216	86.96
0148	排序链表	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Sorting, Two_Pointers, Linked_List, Divide_and_Conquer, Merge_Sort, Big_O_Time_O(log(N))_Space_O(log(N))	820	61.70

Day 5 Greedy


2131	连接两字母单词得到的最长回文串	Medium	Array, String, Hash_Table, Greedy, Counting	607	90.00
0621	任务调度器	Medium	Array, Hash_Table, Sorting, Greedy, Heap_Priority_Queue, Counting	266	98.36

Day 6 Tree


0226	翻转二叉树	Easy	Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	233	54.90
0110	平衡二叉树	Easy	Depth_First_Search, Tree, Binary_Tree	182	71.30

Day 7 Tree


0543	二叉树的直径	Easy	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	307	43.93
0437	路径总和 III	Medium	Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	403	54.12

Day 8 Binary Search


0074	搜索二维矩阵	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Big_O_Time_O(endRow+endCol)_Space_O(1)	159	74.46
0033	搜索旋转排序数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	151	93.77

Day 9 Binary Search Tree


0108	将有序数组转换为二叉搜索树	Easy	Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer	167	80.29
0230	二叉搜索树中第K小的元素	Medium	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(n)_Space_O(n)	393	33.33
0173	二叉搜索树迭代器	Medium	Tree, Binary_Tree, Stack, Design, Binary_Search_Tree, Iterator	563	46.91

Day 10 Graph/BFS/DFS


0994	腐烂的橘子	Medium	Top_100_Liked_Questions, Array, Breadth_First_Search, Matrix	164	82.95
0417	太平洋大西洋水流问题	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix	319	100.00

Day 11 Graph/BFS/DFS


0210	课程表 II	Medium	Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Graph, Topological_Sort	266	96.32
0815	公交路线	Hard	Array, Hash_Table, Breadth_First_Search	429	100.00

Day 12 Dynamic Programming


0198	打家劫舍	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	156	92.24
0322	零钱兑换	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Breadth_First_Search, Big_O_Time_O(m*n)_Space_O(amount)	332	50.68

Day 13 Dynamic Programming


0416	分割等和子集	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Big_O_Time_O(nsums)_Space_O(nsums)	204	98.82
0152	乘积最大子数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	253	88.42

Day 14 Sliding Window/Two Pointer


0003	无重复字符的最长子串	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n)_Space_O(1)	201	87.28
0016	最接近的三数之和	Medium	Array, Sorting, Two_Pointers	163	100.00
0076	最小覆盖子串	Hard	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(s.length())_Space_O(1)	191	96.38

Day 15 Tree


0100	相同的树	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	134	86.63
0101	对称二叉树	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(log(N))	153	82.35
0199	二叉树的右视图	Medium	Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	194	92.89

Day 16 Design


0232	用栈实现队列	Easy	Stack, Design, Queue	258	70.86
0155	最小栈	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Stack, Design, Big_O_Time_O(1)_Space_O(N)	331	84.88
0208	实现 Trie (前缀树)	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Design, Trie, Big_O_Time_O(word.length())_or_O(prefix.length())_Space_O(N)	689	61.00

Day 17 Interval


0057	插入区间	Medium	Array	249	75.63
0056	合并区间	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Big_O_Time_O(n_log_n)_Space_O(n)	334	80.67

Day 18 Stack


0735	小行星碰撞	Medium	Array, Stack	243	100.00
0227	基本计算器 II	Medium	String, Math, Stack	383	62.50

Day 19 Union Find


0547	省份数量	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	229	79.73
0947	移除最多的同行或同列石头	Medium	Depth_First_Search, Graph, Union_Find	200	100.00

Day 20 Brute Force/Backtracking


0039	组合总和	Medium	Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n)	226	88.89
0046	全排列	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n*n!)_Space_O(n+n!)	188	99.00

Udemy

Udemy Integers


0412	Fizz Buzz	Easy	String, Math, Simulation	307	71.81
0136	只出现一次的数字	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1)	344	83.63
0007	整数反转	Medium	Top_Interview_Questions, Math	149	77.89
0009	回文数	Easy	Math	217	95.34
0172	阶乘后的零	Medium	Top_Interview_Questions, Math	220	67.65
0050	Pow(x, n)	Medium	Top_Interview_Questions, Math, Recursion	172	38.68

Udemy Strings


0344	反转字符串	Easy	String, Two_Pointers, Recursion	445	69.75
0014	最长公共前缀	Easy	Top_100_Liked_Questions, Top_Interview_Questions, String	154	89.70
0187	重复的DNA序列	Medium	String, Hash_Table, Bit_Manipulation, Sliding_Window, Hash_Function, Rolling_Hash	319	79.03
0003	无重复字符的最长子串	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n)_Space_O(1)	201	87.28
0020	有效的括号	Easy	Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Big_O_Time_O(n)_Space_O(n)	137	88.76
0005	最长回文子串	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	162	99.00
0394	字符串解码	Medium	Top_100_Liked_Questions, String, Stack, Recursion, Big_O_Time_O(n)_Space_O(n)	224	64.86
0242	有效的字母异位词	Easy	String, Hash_Table, Sorting	251	87.65
0049	字母异位词分组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n*k_log_k)_Space_O(n)	308	96.34
0151	反转字符串中的单词	Medium	String, Two_Pointers	206	98.90
0273	整数转换英文表示	Hard	String, Math, Recursion	273	82.93

Udemy Binary Search


0704	二分查找	Easy	Top_100_Liked_Questions, Array, Binary_Search	261	77.91
0033	搜索旋转排序数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	151	93.77
0153	寻找旋转排序数组中的最小值	Medium	Top_100_Liked_Questions, Array, Binary_Search, Big_O_Time_O(log_N)_Space_O(log_N)	262	60.96

Udemy Arrays


0121	买卖股票的最佳时机	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	609	94.06
0283	移动零	Easy	Top_100_Liked_Questions, Array, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	516	79.07
0001	两数之和	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n)	202	91.18
0217	存在重复元素	Easy	Top_Interview_Questions, Array, Hash_Table, Sorting	719	73.49
0058	最后一个单词的长度	Easy	String	135	93.67
0605	种花问题	Easy	Array, Greedy	209	85.71
0122	买卖股票的最佳时机 II	Medium	Top_Interview_Questions, Array, Dynamic_Programming, Greedy	197	95.10
0080	删除有序数组中的重复项 II	Medium	Array, Two_Pointers	192	80.67
0189	轮转数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	483	86.95
0055	跳跃游戏	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1)	332	89.35
0075	颜色分类	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	164	64.43
0066	加一	Easy	Top_Interview_Questions, Array, Math	148	98.75
0238	除自身以外数组的乘积	Medium	Top_100_Liked_Questions, Array, Prefix_Sum, Big_O_Time_O(n^2)_Space_O(n)	669	48.96
1291	顺次数	Medium	Enumeration	114	100.00
0448	找到所有数组中消失的数字	Easy	Array, Hash_Table	394	100.00
0442	数组中重复的数据	Medium	Array, Hash_Table	480	73.81
0041	缺失的第一个正数	Hard	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n)	357	97.17
0697	数组的度	Easy	Array, Hash_Table	289	84.62
0532	数组中的 k-diff 数对	Medium	Array, Hash_Table, Sorting, Binary_Search, Two_Pointers	230	84.62
0713	乘积小于 K 的子数组	Medium	Array, Sliding_Window	336	92.11
1007	行相等的最少多米诺旋转	Medium	Array, Greedy	421	50.00
1306	跳跃游戏 III	Medium	Array, Depth_First_Search, Breadth_First_Search	291	100.00
0456	132 模式	Medium	Array, Binary_Search, Stack, Ordered_Set, Monotonic_Stack	434	100.00
0239	滑动窗口最大值	Hard	Top_100_Liked_Questions, Array, Heap_Priority_Queue, Sliding_Window, Queue, Monotonic_Queue, Big_O_Time_O(n*k)_Space_O(n+k)	1059	86.14

Udemy Two Pointers


0392	判断子序列	Easy	String, Dynamic_Programming, Two_Pointers	156	87.74
0125	验证回文串	Easy	Top_Interview_Questions, String, Two_Pointers	353	52.06
0977	有序数组的平方	Easy	Array, Sorting, Two_Pointers	271	77.17
0026	删除有序数组中的重复项	Easy	Top_Interview_Questions, Array, Two_Pointers	249	67.38
0042	接雨水	Hard	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1)	189	99.37
0015	三数之和	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n*log(n))_Space_O(n^2)	493	93.45

Udemy Famous Algorithm


0053	最大子数组和	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1)	510	78.81
0169	多数元素	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Sorting, Counting, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1)	460	51.25

Udemy Sorting Algorithms


0912	排序数组	Medium	Array, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Merge_Sort, Bucket_Sort, Counting_Sort, Radix_Sort	606	98.48

Udemy 2D Arrays/Matrix


0304	二维区域和检索 - 矩阵不可变	Medium	Array, Matrix, Design, Prefix_Sum	1373	85.71
0074	搜索二维矩阵	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Big_O_Time_O(endRow+endCol)_Space_O(1)	159	74.46
0054	Spiral Matrix	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Matrix, Simulation	132	95.12
0048	Rotate Image	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1)	160	90.11
1572	Matrix Diagonal Sum	Easy	Array, Matrix	221	67.61
0073	Set Matrix Zeroes	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Matrix, Big_O_Time_O(m*n)_Space_O(1)	248	97.33
0056	Merge Intervals	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Big_O_Time_O(n_log_n)_Space_O(n)	334	80.67

Udemy Linked List


0114	二叉树展开为链表	Medium	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Big_O_Time_O(N)_Space_O(N)	191	93.10
0445	Add Two Numbers II	Medium	Math, Stack, Linked_List	240	82.61
0328	Odd Even Linked List	Medium	Linked_List	216	86.96
0061	旋转链表	Medium	Two_Pointers, Linked_List	160	92.22
0024	两两交换链表中的节点	Medium	Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(1)	149	44.20
0876	Middle of the Linked List	Easy	Two_Pointers, Linked_List	136	76.52
0142	Linked List Cycle II	Medium	Top_100_Liked_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(N)_Space_O(1)	192	63.39
0141	环形链表	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(N)_Space_O(1)	223	91.85
0206	Reverse Linked List	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1)	279	45.78
0021	合并两个有序链表	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(m+n)_Space_O(m+n)	157	92.24
0160	相交链表	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(M+N)_Space_O(1)	262	83.50
0234	Palindrome Linked List	Easy	Top_100_Liked_Questions, Two_Pointers, Stack, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(1)	641	79.53
0138	Copy List with Random Pointer	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Linked_List, Big_O_Time_O(N)_Space_O(N)	274	80.58
0025	Reverse Nodes in k-Group	Hard	Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(k)	189	67.03
0146	LRU Cache	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Design, Linked_List, Doubly_Linked_List, Big_O_Time_O(1)_Space_O(capacity)	1116	97.93
0707	Design Linked List	Medium	Design, Linked_List	243	100.00

Udemy Tree Stack Queue


0144	二叉树的前序遍历	Easy	Depth_First_Search, Tree, Binary_Tree, Stack	277	37.90
0094	二叉树的中序遍历	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Big_O_Time_O(n)_Space_O(n)	152	66.67
0145	二叉树的后序遍历	Easy	Depth_First_Search, Tree, Binary_Tree, Stack	211	80.00
0102	二叉树的层序遍历	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N)	198	95.14
0103	二叉树的锯齿形层序遍历	Medium	Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree	176	71.62
0108	将有序数组转换为二叉搜索树	Easy	Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer	167	80.29
1008	前序遍历构造二叉搜索树	Medium	Array, Tree, Binary_Tree, Stack, Monotonic_Stack, Binary_Search_Tree	145	100.00
0543	二叉树的直径	Easy	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	307	43.93
0938	二叉搜索树的范围和	Easy	Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree	356	55.36
0100	相同的树	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	134	86.63
0226	翻转二叉树	Easy	Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	233	54.90
0111	二叉树的最小深度	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	525	90.51
0104	二叉树的最大深度	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H)	166	83.53
0110	平衡二叉树	Easy	Depth_First_Search, Tree, Binary_Tree	182	71.30
0701	二叉搜索树中的插入操作	Medium	Tree, Binary_Tree, Binary_Search_Tree	311	79.03
0297	二叉树的序列化与反序列化	Hard	String, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Design	475	78.85
0124	二叉树中的最大路径和	Hard	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N)	331	74.42
0098	验证二叉搜索树	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(N)_Space_O(log(N))	190	61.62
0337	打家劫舍 III	Medium	Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree	282	84.62
0236	二叉树的最近公共祖先	Medium	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	386	45.21
0968	监控二叉树	Hard	Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree	176	100.00

Udemy Trie and Heap


0208	实现 Trie (前缀树)	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Design, Trie, Big_O_Time_O(word.length())_or_O(prefix.length())_Space_O(N)	689	61.00
0745	前缀和后缀搜索	Hard	String, Design, Trie	1638	100.00

Udemy Graph


0200	Number of Islands	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(MN)_Space_O(MN)	252	95.41
0133	Clone Graph	Medium	Hash_Table, Depth_First_Search, Breadth_First_Search, Graph	351	60.91
0417	Pacific Atlantic Water Flow	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix	319	100.00

Udemy Dynamic Programming


0120	Triangle	Medium	Array, Dynamic_Programming	194	97.87
0118	Pascal's Triangle	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming	277	33.22
0119	Pascal's Triangle II	Easy	Array, Dynamic_Programming	157	97.27
0139	Word Break	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Dynamic_Programming, Trie, Memoization, Big_O_Time_O(M+max*N)_Space_O(M+N+max)	197	87.17
0152	Maximum Product Subarray	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	253	88.42
0198	House Robber	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	156	92.24
0213	House Robber II	Medium	Array, Dynamic_Programming	257	59.62
0509	Fibonacci Number	Easy	Dynamic_Programming, Math, Recursion, Memoization	139	82.72
0070	Climbing Stairs	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Memoization, Big_O_Time_O(n)_Space_O(n)	124	71.98
0064	最小路径和	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Matrix, Big_O_Time_O(mn)_Space_O(mn)	164	100.00
0300	最长递增子序列	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Binary_Search, Big_O_Time_O(n*log_n)_Space_O(n)	318	82.28
1143	最长公共子序列	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(nm)_Space_O(nm)	307	38.36
0072	Edit Distance	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(n^2)_Space_O(n2)	182	92.16
0044	Wildcard Matching	Hard	Top_Interview_Questions, String, Dynamic_Programming, Greedy, Recursion	220	84.85
0010	Regular Expression Matching	Hard	Top_Interview_Questions, String, Dynamic_Programming, Recursion, Big_O_Time_O(mn)_Space_O(mn)	171	85.26

Udemy Backtracking/Recursion


0022	括号生成	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Big_O_Time_O(2^n)_Space_O(n)	161	85.45
0039	Combination Sum	Medium	Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n)	226	88.89
0216	Combination Sum III	Medium	Array, Backtracking	175	90.91
0078	Subsets	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Backtracking, Big_O_Time_O(2^n)_Space_O(n*2^n)	171	94.92
0017	Letter Combinations of a Phone Number	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Big_O_Time_O(4^n)_Space_O(n)	155	95.24
0046	Permutations	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n*n!)_Space_O(n+n!)	188	99.00

Udemy Bit Manipulation


0191	位1的个数	Easy	Top_Interview_Questions, Bit_Manipulation	237	68.44
0389	Find the Difference	Easy	String, Hash_Table, Sorting, Bit_Manipulation	256	64.81
0190	Reverse Bits	Easy	Top_Interview_Questions, Bit_Manipulation, Divide_and_Conquer	198	81.82
0461	汉明距离	Easy	Bit_Manipulation	150	96.15
1009	Complement of Base 10 Integer	Easy	Bit_Manipulation	126	72.73
0338	Counting Bits	Easy	Dynamic_Programming, Bit_Manipulation, Big_O_Time_O(num)_Space_O(num)	186	99.26
0371	Sum of Two Integers	Medium	Math, Bit_Manipulation	129	95.45
0029	Divide Two Integers	Medium	Top_Interview_Questions, Math, Bit_Manipulation	144	82.50

Udemy Design


0155	Min Stack	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Stack, Design, Big_O_Time_O(1)_Space_O(N)	331	84.88

Data Structure I

Day 1 Array


0217	Contains Duplicate	Easy	Top_Interview_Questions, Array, Hash_Table, Sorting	719	73.49
0053	Maximum Subarray	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1)	510	78.81

Day 2 Array


0001	Two Sum	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n)	202	91.18
0088	合并两个有序数组	Easy	Top_Interview_Questions, Array, Sorting, Two_Pointers	170	69.74

Day 3 Array


0350	Intersection of Two Arrays II	Easy	Array, Hash_Table, Sorting, Binary_Search, Two_Pointers	321	73.37
0121	Best Time to Buy and Sell Stock	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	609	94.06

Day 4 Array


0566	Reshape the Matrix	Easy	Array, Matrix, Simulation	239	99.05
0118	Pascal's Triangle	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming	277	33.22

Day 5 Array


0036	Valid Sudoku	Medium	Top_Interview_Questions, Array, Hash_Table, Matrix	181	95.15
0074	Search a 2D Matrix	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Big_O_Time_O(endRow+endCol)_Space_O(1)	159	74.46

Day 6 String


0387	First Unique Character in a String	Easy	String, Hash_Table, Counting, Queue	369	82.68
0383	Ransom Note	Easy	String, Hash_Table, Counting	333	79.58
0242	Valid Anagram	Easy	String, Hash_Table, Sorting	251	87.65

Day 7 Linked List


0141	Linked List Cycle	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(N)_Space_O(1)	223	91.85
0021	Merge Two Sorted Lists	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(m+n)_Space_O(m+n)	157	92.24
0203	Remove Linked List Elements	Easy	Linked_List, Recursion	233	91.22

Day 8 Linked List


0206	Reverse Linked List	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1)	279	45.78
0083	删除排序链表中的重复元素	Easy	Linked_List	173	82.42

Day 9 Stack Queue


0020	Valid Parentheses	Easy	Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Big_O_Time_O(n)_Space_O(n)	137	88.76
0232	Implement Queue using Stacks	Easy	Stack, Design, Queue	258	70.86

Day 10 Tree


0144	Binary Tree Preorder Traversal	Easy	Depth_First_Search, Tree, Binary_Tree, Stack	277	37.90
0094	Binary Tree Inorder Traversal	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Big_O_Time_O(n)_Space_O(n)	152	66.67
0145	Binary Tree Postorder Traversal	Easy	Depth_First_Search, Tree, Binary_Tree, Stack	211	80.00

Day 11 Tree


0102	Binary Tree Level Order Traversal	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N)	198	95.14
0104	Maximum Depth of Binary Tree	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H)	166	83.53
0101	Symmetric Tree	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(log(N))	153	82.35

Day 12 Tree


0226	Invert Binary Tree	Easy	Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	233	54.90
0112	Path Sum	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	322	36.41

Day 13 Tree


0700	Search in a Binary Search Tree	Easy	Tree, Binary_Tree, Binary_Search_Tree	251	88.31
0701	Insert into a Binary Search Tree	Medium	Tree, Binary_Tree, Binary_Search_Tree	311	79.03

Day 14 Tree


0098	Validate Binary Search Tree	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(N)_Space_O(log(N))	190	61.62
0653	Two Sum IV - Input is a BST	Easy	Hash_Table, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Two_Pointers, Binary_Search_Tree	231	96.08
0235	Lowest Common Ancestor of a Binary Search Tree	Medium	Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree	404	75.59

Data Structure II

Day 1 Array


0136	Single Number	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1)	344	83.63
0169	Majority Element	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Sorting, Counting, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1)	460	51.25
0015	3Sum	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n*log(n))_Space_O(n^2)	493	93.45

Day 2 Array


0075	Sort Colors	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	164	64.43
0056	Merge Intervals	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Big_O_Time_O(n_log_n)_Space_O(n)	334	80.67
0706	Design HashMap	Easy	Array, Hash_Table, Design, Linked_List, Hash_Function	405	92.11

Day 3 Array


0119	Pascal's Triangle II	Easy	Array, Dynamic_Programming	157	97.27
0048	Rotate Image	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1)	160	90.11
0059	Spiral Matrix II	Medium	Array, Matrix, Simulation	153	41.70

Day 4 Array


0240	Search a 2D Matrix II	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Divide_and_Conquer, Big_O_Time_O(n+m)_Space_O(1)	460	66.08
0435	Non-overlapping Intervals	Medium	Array, Dynamic_Programming, Sorting, Greedy	1040	85.07

Day 5 Array


0334	Increasing Triplet Subsequence	Medium	Array, Greedy	672	60.61
0238	Product of Array Except Self	Medium	Top_100_Liked_Questions, Array, Prefix_Sum, Big_O_Time_O(n^2)_Space_O(n)	669	48.96
0560	和为 K 的子数组	Medium	Top_100_Liked_Questions, Array, Hash_Table, Prefix_Sum, Big_O_Time_O(n)_Space_O(n)	692	53.27

Day 6 String


0415	Add Strings	Easy	String, Math, Simulation	296	76.00
0409	Longest Palindrome	Easy	String, Hash_Table, Greedy	259	60.71

Day 7 String


0290	Word Pattern	Easy	String, Hash_Table	177	89.55
0763	Partition Labels	Medium	String, Hash_Table, Greedy, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	235	84.75

Day 8 String


0049	Group Anagrams	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n*k_log_k)_Space_O(n)	308	96.34
0043	Multiply Strings	Medium	String, Math, Simulation	165	96.72

Day 9 String


0187	Repeated DNA Sequences	Medium	String, Hash_Table, Bit_Manipulation, Sliding_Window, Hash_Function, Rolling_Hash	319	79.03
0005	Longest Palindromic Substring	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	162	99.00

Day 10 Linked List


0002	Add Two Numbers	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Math, Linked_List, Recursion, Big_O_Time_O(max(N,M))_Space_O(max(N,M))	203	96.13
0142	环形链表 II	Medium	Top_100_Liked_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(N)_Space_O(1)	192	63.39

Day 11 Linked List


0160	Intersection of Two Linked Lists	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Two_Pointers, Linked_List, Big_O_Time_O(M+N)_Space_O(1)	262	83.50
0082	删除排序链表中的重复元素 II	Medium	Two_Pointers, Linked_List	166	89.47

Day 12 Linked List


0024	两两交换链表中的节点	Medium	Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(1)	149	44.20
0707	Design Linked List	Medium	Design, Linked_List	243	100.00

Day 13 Linked List


0025	Reverse Nodes in k-Group	Hard	Top_100_Liked_Questions, Linked_List, Recursion, Big_O_Time_O(n)_Space_O(k)	189	67.03
0143	Reorder List	Medium	Two_Pointers, Stack, Linked_List, Recursion	395	82.26

Day 14 Stack Queue


0155	Min Stack	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Stack, Design, Big_O_Time_O(1)_Space_O(N)	331	84.88
1249	Minimum Remove to Make Valid Parentheses	Medium	String, Stack	218	100.00
1823	Find the Winner of the Circular Game	Medium	Array, Math, Simulation, Recursion, Queue	119	87.50

Day 15 Tree


0108	Convert Sorted Array to Binary Search Tree	Easy	Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer	167	80.29
0105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Big_O_Time_O(N)_Space_O(N)	183	95.45
0103	Binary Tree Zigzag Level Order Traversal	Medium	Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree	176	71.62

Day 16 Tree


0199	Binary Tree Right Side View	Medium	Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	194	92.89
0113	Path Sum II	Medium	Depth_First_Search, Tree, Binary_Tree, Backtracking	364	78.67
0450	Delete Node in a BST	Medium	Tree, Binary_Tree, Binary_Search_Tree	257	84.62

Day 17 Tree


0230	Kth Smallest Element in a BST	Medium	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(n)_Space_O(n)	393	33.33
0173	Binary Search Tree Iterator	Medium	Tree, Binary_Tree, Stack, Design, Binary_Search_Tree, Iterator	563	46.91

Day 18 Tree


0236	二叉树的最近公共祖先	Medium	Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n)	386	45.21
0297	Serialize and Deserialize Binary Tree	Hard	String, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Design	475	78.85

Day 19 Graph


0997	Find the Town Judge	Easy	Array, Hash_Table, Graph	475	58.62
1557	Minimum Number of Vertices to Reach All Nodes	Medium	Graph	792	99.29
0841	Keys and Rooms	Medium	Depth_First_Search, Breadth_First_Search, Graph	189	69.23

Day 20 Heap Priority Queue


0215	Kth Largest Element in an Array	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Quickselect, Big_O_Time_O(n*log(n))_Space_O(log(n))	839	34.43
0347	Top K Frequent Elements	Medium	Top_100_Liked_Questions, Array, Hash_Table, Sorting, Heap_Priority_Queue, Counting, Divide_and_Conquer, Quickselect, Bucket_Sort, Big_O_Time_O(n*log(n))_Space_O(k)	268	99.74

Day 21 Heap Priority Queue


0451	Sort Characters By Frequency	Medium	String, Hash_Table, Sorting, Heap_Priority_Queue, Counting, Bucket_Sort	288	81.72
0973	K Closest Points to Origin	Medium	Array, Math, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Geometry, Quickselect	800	37.89

Algorithm I

Day 1 Binary Search


0704	Binary Search	Easy	Top_100_Liked_Questions, Array, Binary_Search	261	77.91
0278	First Bad Version	Easy	Binary_Search, Interactive	349	76.86
0035	Search Insert Position	Easy	Top_100_Liked_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	159	93.03

Day 2 Two Pointers


0977	Squares of a Sorted Array	Easy	Array, Sorting, Two_Pointers	271	77.17
0189	轮转数组/旋转数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	483	86.95

Day 3 Two Pointers


0283	Move Zeroes	Easy	Top_100_Liked_Questions, Array, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	516	79.07
0167	Two Sum II - Input Array Is Sorted	Medium	Array, Binary_Search, Two_Pointers	403	68.74

Day 4 Two Pointers


0344	Reverse String	Easy	String, Two_Pointers, Recursion	445	69.75
0557	Reverse Words in a String III	Easy	String, Two_Pointers	215	98.10

Day 5 Two Pointers


0876	Middle of the Linked List	Easy	Two_Pointers, Linked_List	136	76.52
0019	删除链表的倒数第 N 个结点	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Two_Pointers, Linked_List, Big_O_Time_O(L)_Space_O(L)	144	96.28

Day 6 Sliding Window


0003	Longest Substring Without Repeating Characters	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n)_Space_O(1)	201	87.28
0567	Permutation in String	Medium	Top_100_Liked_Questions, String, Hash_Table, Two_Pointers, Sliding_Window	169	100.00

Day 7 Breadth First Search Depth First Search


0733	Flood Fill	Easy	Array, Depth_First_Search, Breadth_First_Search, Matrix	230	97.76
0695	Max Area of Island	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	181	93.83

Day 8 Breadth First Search Depth First Search


0617	合并二叉树	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	243	72.83
0116	填充每个节点的下一个右侧节点指针	Medium	Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Linked_List	355	69.02

Day 9 Breadth First Search Depth First Search


0542	01 Matrix	Medium	Array, Dynamic_Programming, Breadth_First_Search, Matrix	441	94.06
0994	Rotting Oranges	Medium	Top_100_Liked_Questions, Array, Breadth_First_Search, Matrix	164	82.95

Day 10 Recursion Backtracking


0021	Merge Two Sorted Lists	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(m+n)_Space_O(m+n)	157	92.24
0206	Reverse Linked List	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Linked_List, Recursion, Big_O_Time_O(N)_Space_O(1)	279	45.78

Day 11 Recursion Backtracking


0077	Combinations	Medium	Backtracking	232	100.00
0046	Permutations	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n*n!)_Space_O(n+n!)	188	99.00
0784	Letter Case Permutation	Medium	String, Bit_Manipulation, Backtracking	219	84.62

Day 12 Dynamic Programming


0070	Climbing Stairs	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Memoization, Big_O_Time_O(n)_Space_O(n)	124	71.98
0198	打家劫舍	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	156	92.24
0120	Triangle	Medium	Array, Dynamic_Programming	194	97.87

Day 13 Bit Manipulation


0231	Power of Two	Easy	Math, Bit_Manipulation, Recursion	161	86.81
0191	Number of 1 Bits	Easy	Top_Interview_Questions, Bit_Manipulation	237	68.44

Day 14 Bit Manipulation


0190	Reverse Bits	Easy	Top_Interview_Questions, Bit_Manipulation, Divide_and_Conquer	198	81.82
0136	Single Number	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Big_O_Time_O(N)_Space_O(1)	344	83.63

Algorithm II

Day 1 Binary Search


0034	Find First and Last Position of Element in Sorted Array	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	174	100.00
0033	Search in Rotated Sorted Array	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	151	93.77
0074	Search a 2D Matrix	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Big_O_Time_O(endRow+endCol)_Space_O(1)	159	74.46

Day 2 Binary Search


0153	Find Minimum in Rotated Sorted Array	Medium	Top_100_Liked_Questions, Array, Binary_Search, Big_O_Time_O(log_N)_Space_O(log_N)	262	60.96
0162	Find Peak Element	Medium	Top_Interview_Questions, Array, Binary_Search	297	53.85

Day 3 Two Pointers


0082	删除排序链表中的重复元素 II	Medium	Two_Pointers, Linked_List	166	89.47
0015	3Sum	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n*log(n))_Space_O(n^2)	493	93.45

Day 4 Two Pointers


0844	Backspace String Compare	Easy	String, Two_Pointers, Stack, Simulation	126	98.31
0986	Interval List Intersections	Medium	Array, Two_Pointers	318	60.98
0011	Container With Most Water	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Greedy, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	402	78.57

Day 5 Sliding Window


0438	Find All Anagrams in a String	Medium	Top_100_Liked_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n+m)_Space_O(1)	561	54.68
0713	Subarray Product Less Than K	Medium	Array, Sliding_Window	336	92.11
0209	Minimum Size Subarray Sum	Medium	Array, Binary_Search, Prefix_Sum, Sliding_Window	315	96.73

Day 6 Breadth First Search Depth First Search


0200	Number of Islands	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(MN)_Space_O(MN)	252	95.41
0547	Number of Provinces	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	229	79.73

Day 7 Breadth First Search Depth First Search


0117	Populating Next Right Pointers in Each Node II	Medium	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Linked_List	199	94.67
0572	Subtree of Another Tree	Easy	Depth_First_Search, Tree, Binary_Tree, Hash_Function, String_Matching	214	92.39

Day 8 Breadth First Search Depth First Search


1091	Shortest Path in Binary Matrix	Medium	Array, Breadth_First_Search, Matrix	305	98.28
0130	Surrounded Regions	Medium	Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	355	84.42
0797	All Paths From Source to Target	Medium	Depth_First_Search, Breadth_First_Search, Graph, Backtracking	232	100.00

Day 9 Recursion Backtracking


0078	Subsets	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Bit_Manipulation, Backtracking, Big_O_Time_O(2^n)_Space_O(n*2^n)	171	94.92
0090	Subsets II	Medium	Array, Bit_Manipulation, Backtracking	200	88.33

Day 10 Recursion Backtracking


0047	Permutations II	Medium	Array, Backtracking	199	100.00
0039	Combination Sum	Medium	Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n)	226	88.89
0040	Combination Sum II	Medium	Array, Backtracking	217	93.75

Day 11 Recursion Backtracking


0017	Letter Combinations of a Phone Number	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Big_O_Time_O(4^n)_Space_O(n)	155	95.24
0022	Generate Parentheses	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Big_O_Time_O(2^n)_Space_O(n)	161	85.45
0079	Word Search	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Matrix, Backtracking, Big_O_Time_O(4^(mn))_Space_O(mn)	392	72.92

Day 12 Dynamic Programming


0213	打家劫舍 II	Medium	Array, Dynamic_Programming	257	59.62
0055	跳跃游戏	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1)	332	89.35

Day 13 Dynamic Programming


0045	跳跃游戏 II	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1)	208	93.37
0062	不同路径	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Combinatorics, Big_O_Time_O(mn)_Space_O(mn)	118	94.65

Day 14 Dynamic Programming


0005	最长回文子串	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	162	99.00
0413	Arithmetic Slices	Medium	Array, Dynamic_Programming	156	100.00

Day 15 Dynamic Programming


0091	Decode Ways	Medium	Top_Interview_Questions, String, Dynamic_Programming	148	79.07
0139	Word Break	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Dynamic_Programming, Trie, Memoization, Big_O_Time_O(M+max*N)_Space_O(M+N+max)	197	87.17

Day 16 Dynamic Programming


0300	最长递增子序列	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Binary_Search, Big_O_Time_O(n*log_n)_Space_O(n)	318	82.28
0673	最长递增子序列的个数	Medium	Array, Dynamic_Programming, Segment_Tree, Binary_Indexed_Tree	226	91.67

Day 17 Dynamic Programming


1143	最长公共子序列	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(nm)_Space_O(nm)	307	38.36
0583	两个字符串的删除操作	Medium	String, Dynamic_Programming	197	100.00

Day 18 Dynamic Programming


0072	编辑距离	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(n^2)_Space_O(n2)	182	92.16
0322	零钱兑换	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Breadth_First_Search, Big_O_Time_O(m*n)_Space_O(amount)	332	50.68
0343	整数拆分	Medium	Dynamic_Programming, Math	218	63.89

Day 19 Bit Manipulation


0201	数字范围按位与	Medium	Bit_Manipulation	368	80.00

Day 20 Others


0384	打乱数组	Medium	Array, Math, Randomized	940	72.09

Day 21 Others


0202	快乐数	Easy	Top_Interview_Questions, Hash_Table, Math, Two_Pointers	261	45.08
0149	直线上最多的点数	Hard	Top_Interview_Questions, Array, Hash_Table, Math, Geometry	307	83.33

Binary Search I

Day 1


0704	二分查找	Easy	Top_100_Liked_Questions, Array, Binary_Search	261	77.91
0374	猜数字大小	Easy	Binary_Search, Interactive	134	94.19

Day 2


0035	搜索插入位置	Easy	Top_100_Liked_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	159	93.03
0852	山脉数组的峰顶索引	Medium	Array, Binary_Search	433	94.29

Day 3


0367	有效的完全平方数	Easy	Math, Binary_Search	137	94.55
1385	两个数组间的距离值	Easy	Array, Sorting, Binary_Search, Two_Pointers	190	84.62

Day 4


0069	x 的平方根	Easy	Top_Interview_Questions, Math, Binary_Search	140	94.72
0744	寻找比目标字母大的最小字母	Easy	Array, Binary_Search	162	100.00

Day 5


0278	第一个错误的版本	Easy	Binary_Search, Interactive	349	76.86
0034	在排序数组中查找元素的第一个和最后一个位置	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	174	100.00

Day 6


0441	排列硬币	Easy	Math, Binary_Search	150	84.21
1539	第 k 个缺失的正整数	Easy	Array, Binary_Search	153	100.00

Day 7


0167	两数之和 II - 输入有序数组	Medium	Array, Binary_Search, Two_Pointers	403	68.74
1608	特殊数组的特征值	Easy	Array, Sorting, Binary_Search	147	81.82

Day 8


1351	Count Negative Numbers in a Sorted Matrix	Easy	Array, Binary_Search, Matrix	206	71.43
0074	Search a 2D Matrix	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Big_O_Time_O(endRow+endCol)_Space_O(1)	159	74.46

Day 9


1337	The K Weakest Rows in a Matrix	Easy	Array, Sorting, Binary_Search, Matrix, Heap_Priority_Queue	216	77.59
1346	Check If N and Its Double Exist	Easy	Array, Hash_Table, Sorting, Binary_Search, Two_Pointers	175	70.83

Day 10


0350	Intersection of Two Arrays II	Easy	Array, Hash_Table, Sorting, Binary_Search, Two_Pointers	321	73.37
0633	Sum of Square Numbers	Medium	Math, Binary_Search, Two_Pointers	126	100.00

Day 11


1855	Maximum Distance Between a Pair of Values	Medium	Array, Greedy, Binary_Search, Two_Pointers	458	100.00
0033	搜索旋转排序数组	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Big_O_Time_O(log_n)_Space_O(1)	151	93.77

Day 12


0153	寻找旋转排序数组中的最小值	Medium	Top_100_Liked_Questions, Array, Binary_Search, Big_O_Time_O(log_N)_Space_O(log_N)	262	60.96

Binary Search II

Day 1


0209	长度最小的子数组	Medium	Array, Binary_Search, Prefix_Sum, Sliding_Window	315	96.73
0611	有效三角形的个数	Medium	Array, Sorting, Greedy, Binary_Search, Two_Pointers	203	100.00

Day 2


0658	找到 K 个最接近的元素	Medium	Array, Sorting, Binary_Search, Two_Pointers, Heap_Priority_Queue	375	95.16
1894	Find the Student that Will Replace the Chalk	Medium	Array, Binary_Search, Simulation, Prefix_Sum	520	50.00

Day 3


0300	最长递增子序列	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Binary_Search, Big_O_Time_O(n*log_n)_Space_O(n)	318	82.28
1760	Minimum Limit of Balls in a Bag	Medium	Array, Binary_Search	460	100.00

Day 4


0875	Koko Eating Bananas	Medium	Array, Binary_Search	267	93.85
1552	Magnetic Force Between Two Balls	Medium	Array, Sorting, Binary_Search	636	100.00

Day 5


0287	Find the Duplicate Number	Medium	Top_100_Liked_Questions, Array, Binary_Search, Two_Pointers, Bit_Manipulation, Big_O_Time_O(n)_Space_O(n)	656	66.21
1283	Find the Smallest Divisor Given a Threshold	Medium	Array, Binary_Search	255	100.00

Day 6


1898	Maximum Number of Removable Characters	Medium	Array, String, Binary_Search	636	100.00
1870	Minimum Speed to Arrive on Time	Medium	Array, Binary_Search	628	50.00

Day 7


1482	Minimum Number of Days to Make m Bouquets	Medium	Array, Binary_Search	538	50.00
1818	Minimum Absolute Sum Difference	Medium	Array, Sorting, Binary_Search, Ordered_Set	447	100.00

Day 8


0240	Search a 2D Matrix II	Medium	Top_100_Liked_Questions, Array, Binary_Search, Matrix, Divide_and_Conquer, Big_O_Time_O(n+m)_Space_O(1)	460	66.08
0275	H-Index II	Medium	Array, Binary_Search	398	81.82

Day 9


1838	Frequency of the Most Frequent Element	Medium	Array, Sorting, Greedy, Binary_Search, Prefix_Sum, Sliding_Window	564	88.89
0540	Single Element in a Sorted Array	Medium	Array, Binary_Search	274	86.67

Day 10


0222	Count Complete Tree Nodes
1712	Ways to Split Array Into Three Subarrays	Medium	Array, Binary_Search, Two_Pointers, Prefix_Sum	486	100.00

Day 11


0826	Most Profit Assigning Work	Medium	Array, Sorting, Greedy, Binary_Search, Two_Pointers	366	100.00
0436	Find Right Interval	Medium	Array, Sorting, Binary_Search	333	100.00

Day 12


0081	Search in Rotated Sorted Array II	Medium	Array, Binary_Search	170	96.30
0162	Find Peak Element	Medium	Top_Interview_Questions, Array, Binary_Search	297	53.85

Day 13


0154	Find Minimum in Rotated Sorted Array II	Hard	Array, Binary_Search	275	84.00
0528	Random Pick with Weight	Medium	Math, Binary_Search, Prefix_Sum, Randomized	393	91.38

Day 14


1508	Range Sum of Sorted Subarray Sums	Medium	Array, Sorting, Binary_Search, Two_Pointers	378	66.67
1574	Shortest Subarray to be Removed to Make Array Sorted	Medium	Array, Binary_Search, Two_Pointers, Stack, Monotonic_Stack	477	50.00

Day 15


1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold	Medium	Array, Binary_Search, Matrix, Prefix_Sum	376	100.00
1498	Number of Subsequences That Satisfy the Given Sum Condition	Medium	Array, Sorting, Binary_Search, Two_Pointers	487	97.89

Day 16


0981	Time Based Key-Value Store	Medium	String, Hash_Table, Binary_Search, Design	1011	65.56
1300	Sum of Mutated Array Closest to Target	Medium	Array, Sorting, Binary_Search	217	100.00

Day 17


1802	Maximum Value at a Given Index in a Bounded Array	Medium	Greedy, Binary_Search	118	100.00
1901	Find a Peak Element II	Medium	Array, Binary_Search, Matrix, Divide_and_Conquer	726	100.00

Day 18


1146	Snapshot Array	Medium	Array, Hash_Table, Binary_Search, Design	1064	57.14
1488	Avoid Flood in The City	Medium	Array, Hash_Table, Greedy, Binary_Search, Heap_Priority_Queue	823	66.67

Day 19


1562	Find Latest Group of Size M	Medium	Array, Binary_Search, Simulation	534	100.00
1648	Sell Diminishing-Valued Colored Balls	Medium	Array, Math, Sorting, Greedy, Binary_Search, Heap_Priority_Queue	509	100.00

Day 20


1201	Ugly Number III	Medium	Math, Binary_Search, Number_Theory	136	100.00
0911	Online Election	Medium	Array, Hash_Table, Binary_Search, Design	766	83.33

Dynamic Programming I

Day 1


0509	Fibonacci Number	Easy	Dynamic_Programming, Math, Recursion, Memoization	139	82.72
1137	N-th Tribonacci Number	Easy	Dynamic_Programming, Math, Memoization	122	69.35

Day 2


0070	Climbing Stairs	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Memoization, Big_O_Time_O(n)_Space_O(n)	124	71.98
0746	Min Cost Climbing Stairs	Easy	Array, Dynamic_Programming	171	96.76

Day 3


0198	House Robber	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	156	92.24
0213	House Robber II	Medium	Array, Dynamic_Programming	257	59.62
0740	Delete and Earn	Medium	Array, Hash_Table, Dynamic_Programming	192	100.00

Day 4


0055	Jump Game	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1)	332	89.35
0045	Jump Game II	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1)	208	93.37

Day 5


0053	Maximum Subarray	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1)	510	78.81
0918	Maximum Sum Circular Subarray	Medium	Array, Dynamic_Programming, Divide_and_Conquer, Queue, Monotonic_Queue	339	86.96

Day 6


0152	Maximum Product Subarray	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	253	88.42
1567	Maximum Length of Subarray With Positive Product	Medium	Array, Dynamic_Programming, Greedy	468	33.33

Day 7


1014	Best Sightseeing Pair	Medium	Array, Dynamic_Programming	336	66.67
0121	Best Time to Buy and Sell Stock	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Big_O_Time_O(N)_Space_O(1)	609	94.06
0122	Best Time to Buy and Sell Stock II	Medium	Top_Interview_Questions, Array, Dynamic_Programming, Greedy	197	95.10

Day 8


0309	买卖股票的最佳时机含冷冻期	Medium	Array, Dynamic_Programming	272	73.33
0714	买卖股票的最佳时机含手续费	Medium	Array, Dynamic_Programming, Greedy	417	90.91

Day 9


0139	Word Break	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Dynamic_Programming, Trie, Memoization, Big_O_Time_O(M+max*N)_Space_O(M+N+max)	197	87.17
0042	接雨水	Hard	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1)	189	99.37

Day 10


0413	Arithmetic Slices	Medium	Array, Dynamic_Programming	156	100.00
0091	Decode Ways	Medium	Top_Interview_Questions, String, Dynamic_Programming	148	79.07

Day 11


0264	Ugly Number II	Medium	Hash_Table, Dynamic_Programming, Math, Heap_Priority_Queue	182	95.45
0096	Unique Binary Search Trees	Medium	Dynamic_Programming, Math, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(n)_Space_O(1)	116	92.31

Day 12


0118	Pascal's Triangle	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming	277	33.22
0119	Pascal's Triangle II	Easy	Array, Dynamic_Programming	157	97.27

Day 13


0931	Minimum Falling Path Sum	Medium	Array, Dynamic_Programming, Matrix	201	84.21
0120	Triangle	Medium	Array, Dynamic_Programming	194	97.87

Day 14


1314	Matrix Block Sum	Medium	Array, Matrix, Prefix_Sum	235	100.00
0304	Range Sum Query 2D - Immutable	Medium	Array, Matrix, Design, Prefix_Sum	1373	85.71

Day 15


0062	Unique Paths	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Math, Combinatorics, Big_O_Time_O(mn)_Space_O(mn)	118	94.65
0063	不同路径 II	Medium	Array, Dynamic_Programming, Matrix	151	81.94

Day 16


0064	最小路径和	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Matrix, Big_O_Time_O(mn)_Space_O(mn)	164	100.00
0221	Maximal Square	Medium	Array, Dynamic_Programming, Matrix, Big_O_Time_O(mn)_Space_O(mn)	614	44.00

Day 17


0005	Longest Palindromic Substring	Medium	Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n)	162	99.00
0516	Longest Palindromic Subsequence	Medium	String, Dynamic_Programming	243	87.50

Day 18


0300	Longest Increasing Subsequence	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Binary_Search, Big_O_Time_O(n*log_n)_Space_O(n)	318	82.28
0376	Wiggle Subsequence	Medium	Array, Dynamic_Programming, Greedy	162	88.89

Day 19


0392	Is Subsequence	Easy	String, Dynamic_Programming, Two_Pointers	156	87.74
1143	Longest Common Subsequence	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(nm)_Space_O(nm)	307	38.36
0072	Edit Distance	Medium	Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(n^2)_Space_O(n2)	182	92.16

Day 20


0322	Coin Change	Medium	Top_100_Liked_Questions, Array, Dynamic_Programming, Breadth_First_Search, Big_O_Time_O(m*n)_Space_O(amount)	332	50.68
0518	Coin Change II	Medium	Array, Dynamic_Programming	139	100.00

Day 21


0377	组合总和 Ⅳ	Medium	Array, Dynamic_Programming	217	72.41
0343	Integer Break	Medium	Dynamic_Programming, Math	218	63.89
0279	Perfect Squares	Medium	Dynamic_Programming, Math, Breadth_First_Search	176	98.80

Programming Skills I

Day 1 Basic Data Type


1523	Count Odd Numbers in an Interval Range	Easy	Math	114	97.22
1491	Average Salary Excluding the Minimum and Maximum Salary	Easy	Array, Sorting	137	91.67

Day 2 Operator


0191	Number of 1 Bits	Easy	Top_Interview_Questions, Bit_Manipulation	237	68.44
1281	Subtract the Product and Sum of Digits of an Integer	Easy	Math	128	61.82

Day 3 Conditional Statements


0976	Largest Perimeter Triangle	Easy	Array, Math, Sorting, Greedy	304	33.33
1779	Find Nearest Point That Has the Same X or Y Coordinate	Easy	Array	364	100.00

Day 4 Loop


1822	Sign of the Product of an Array	Easy	Array, Math	170	92.51
1502	Can Make Arithmetic Progression From Sequence	Easy	Array, Sorting	156	94.82
0202	Happy Number	Easy	Top_Interview_Questions, Hash_Table, Math, Two_Pointers	261	45.08
1790	Check if One String Swap Can Make Strings Equal	Easy	String, Hash_Table, Counting	138	100.00

Day 5 Function


0589	N-ary Tree Preorder Traversal	Easy	Depth_First_Search, Tree, Stack	233	84.02
0496	Next Greater Element I	Easy	Array, Hash_Table, Stack, Monotonic_Stack	171	100.00
1232	Check If It Is a Straight Line	Easy	Array, Math, Geometry	152	95.38

Day 6 Array


1588	Sum of All Odd Length Subarrays	Easy	Array, Math, Prefix_Sum	157	64.00
0283	Move Zeroes	Easy	Top_100_Liked_Questions, Array, Two_Pointers, Big_O_Time_O(n)_Space_O(1)	516	79.07
1672	Richest Customer Wealth	Easy	Array, Matrix	155	94.54

Day 7 Array


1572	Matrix Diagonal Sum	Easy	Array, Matrix	221	67.61
0566	Reshape the Matrix	Easy	Array, Matrix, Simulation	239	99.05

Day 8 String


1768	Merge Strings Alternately	Easy	String, Two_Pointers	138	93.81
1678	Goal Parser Interpretation	Easy	String	136	88.24
0389	Find the Difference	Easy	String, Hash_Table, Sorting, Bit_Manipulation	256	64.81

Day 9 String


0709	To Lower Case	Easy	String	142	98.68
1309	Decrypt String from Alphabet to Integer Mapping	Easy	String	129	95.45
0953	Verifying an Alien Dictionary	Easy	Array, String, Hash_Table	137	100.00

Day 10 Linked List and Tree


1290	Convert Binary Number in a Linked List to Integer	Easy	Math, Linked_List	138	65.79
0876	Middle of the Linked List	Easy	Two_Pointers, Linked_List	136	76.52
0104	Maximum Depth of Binary Tree	Easy	Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H)	166	83.53
0404	Sum of Left Leaves	Easy	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree	173	86.05

Day 11 Containers and Libraries


1356	Sort Integers by The Number of 1 Bits	Easy	Array, Sorting, Bit_Manipulation, Counting	236	92.31
0232	Implement Queue using Stacks	Easy	Stack, Design, Queue	258	70.86
0242	Valid Anagram	Easy	String, Hash_Table, Sorting	251	87.65
0217	Contains Duplicate	Easy	Top_Interview_Questions, Array, Hash_Table, Sorting	719	73.49

Day 12 Class and Object


1603	Design Parking System	Easy	Design, Simulation, Counting	376	31.83
0303	Range Sum Query - Immutable	Easy	Array, Design, Prefix_Sum	472	63.64

Programming Skills II

Day 1


0896	Monotonic Array	Easy	Array	576	90.91
0028	Find the Index of the First Occurrence in a String	Easy	Top_Interview_Questions, String, Two_Pointers, String_Matching	126	97.58

Day 2


0110	Balanced Binary Tree	Easy	Depth_First_Search, Tree, Binary_Tree	182	71.30
0459	Repeated Substring Pattern	Easy	String, String_Matching	201	100.00

Day 3


0150	逆波兰表达式求值	Medium	Top_Interview_Questions, Array, Math, Stack	233	88.82
0066	Plus One	Easy	Top_Interview_Questions, Array, Math	148	98.75

Day 4


1367	Linked List in Binary Tree	Medium	Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Linked_List	237	92.86
0043	Multiply Strings	Medium	String, Math, Simulation	165	96.72

Day 5


0067	Add Binary	Easy	String, Math, Bit_Manipulation, Simulation	164	90.60
0989	Add to Array-Form of Integer	Easy	Array, Math	350	70.00

Day 6


0739	每日温度	Medium	Top_100_Liked_Questions, Array, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(n)	936	80.54
0058	最后一个单词的长度	Easy	String	135	93.67

Day 7


0048	旋转图像	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1)	160	90.11
1886	判断矩阵经轮转后是否一致	Easy	Array, Matrix	147	85.71

Day 8


0054	螺旋矩阵	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Matrix, Simulation	132	95.12
0973	最接近原点的 K 个点	Medium	Array, Math, Sorting, Heap_Priority_Queue, Divide_and_Conquer, Geometry, Quickselect	800	37.89

Day 9


1630	等差子数组	Medium	Array, Sorting	264	100.00
0429	N-ary Tree Level Order Traversal	Medium	Breadth_First_Search, Tree	248	75.86

Day 10


0503	Next Greater Element II	Medium	Array, Stack, Monotonic_Stack	331	92.68
0556	Next Greater Element III	Medium	String, Math, Two_Pointers	137	80.00

Day 11


1376	Time Needed to Inform All Employees	Medium	Depth_First_Search, Breadth_First_Search, Tree	915	37.62
0049	Group Anagrams	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n*k_log_k)_Space_O(n)	308	96.34

Day 12


0438	Find All Anagrams in a String	Medium	Top_100_Liked_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n+m)_Space_O(1)	561	54.68
0713	Subarray Product Less Than K	Medium	Array, Sliding_Window	336	92.11

Day 13


0304	Range Sum Query 2D - Immutable	Medium	Array, Matrix, Design, Prefix_Sum	1373	85.71
0910	Smallest Range II	Medium	Array, Math, Sorting, Greedy	234	100.00

Day 14


0143	Reorder List	Medium	Two_Pointers, Stack, Linked_List, Recursion	395	82.26
0138	随机链表的复制	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Hash_Table, Linked_List, Big_O_Time_O(N)_Space_O(N)	274	80.58

Day 15


0002	Add Two Numbers	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Math, Linked_List, Recursion, Big_O_Time_O(max(N,M))_Space_O(max(N,M))	203	96.13
0445	Add Two Numbers II	Medium	Math, Stack, Linked_List	240	82.61

Day 16


0061	Rotate List	Medium	Two_Pointers, Linked_List	160	92.22
0173	Binary Search Tree Iterator	Medium	Tree, Binary_Tree, Stack, Design, Binary_Search_Tree, Iterator	563	46.91

Day 17


1845	Seat Reservation Manager	Medium	Design, Heap_Priority_Queue	834	100.00
0860	Lemonade Change	Easy	Array, Greedy	413	86.96

Day 18


0155	Min Stack	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Stack, Design, Big_O_Time_O(1)_Space_O(N)	331	84.88
0341	Flatten Nested List Iterator	Medium	Depth_First_Search, Tree, Stack, Design, Queue, Iterator	210	100.00

Day 19


1797	Design Authentication Manager	Medium	Hash_Table, Design	334	100.00
0707	Design Linked List	Medium	Design, Linked_List	243	100.00

Day 20


0380	Insert Delete GetRandom O(1)	Medium	Array, Hash_Table, Math, Design, Randomized	1326	68.23
0622	Design Circular Queue	Medium	Array, Design, Linked_List, Queue	234	92.68
0729	My Calendar I	Medium	Binary_Search, Design, Ordered_Set, Segment_Tree	378	69.70

Graph Theory I

Day 1 Matrix Related Problems


0733	Flood Fill	Easy	Array, Depth_First_Search, Breadth_First_Search, Matrix	230	97.76
0200	Number of Islands	Medium	Top_100_Liked_Questions, Top_Interview_Questions, Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find, Big_O_Time_O(MN)_Space_O(MN)	252	95.41

Day 2 Matrix Related Problems


0695	Max Area of Island	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	181	93.83
1254	Number of Closed Islands	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	177	89.47

Day 3 Matrix Related Problems


1020	Number of Enclaves	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	283	90.70
1905	Count Sub Islands	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix, Union_Find	866	100.00

Day 4 Matrix Related Problems


1162	As Far from Land as Possible	Medium	Array, Dynamic_Programming, Breadth_First_Search, Matrix	362	81.25
0417	Pacific Atlantic Water Flow	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix	319	100.00

Day 5 Matrix Related Problems


1091	Shortest Path in Binary Matrix	Medium	Array, Breadth_First_Search, Matrix	305	98.28
0542	01 Matrix	Medium	Array, Dynamic_Programming, Breadth_First_Search, Matrix	441	94.06

Day 6 Matrix Related Problems


0934	Shortest Bridge	Medium	Array, Depth_First_Search, Breadth_First_Search, Matrix	301	80.95
1926	Nearest Exit from Entrance in Maze	Medium	Array, Breadth_First_Search, Matrix	351	94.44

Day 7 Standard Traversal


0797	All Paths From Source to Target	Medium	Depth_First_Search, Breadth_First_Search, Graph, Backtracking	232	100.00
0841	Keys and Rooms	Medium	Depth_First_Search, Breadth_First_Search, Graph	189	69.23

Day 8 Standard Traversal


0547	Number of Provinces	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	229	79.73
1319	Number of Operations to Make Network Connected	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	379	83.33

Day 9 Standard Traversal


1376	Time Needed to Inform All Employees	Medium	Depth_First_Search, Breadth_First_Search, Tree	915	37.62
0802	Find Eventual Safe States	Medium	Depth_First_Search, Breadth_First_Search, Graph, Topological_Sort	511	100.00

Day 10 Standard Traversal


1129	Shortest Path with Alternating Colors	Medium	Breadth_First_Search, Graph	208	80.00
1466	Reorder Routes to Make All Paths Lead to the City Zero	Medium	Depth_First_Search, Breadth_First_Search, Graph	718	100.00
0847	Shortest Path Visiting All Nodes	Hard	Dynamic_Programming, Breadth_First_Search, Bit_Manipulation, Graph, Bitmask	164	100.00

Day 11 Breadth First Search


1306	Jump Game III	Medium	Array, Depth_First_Search, Breadth_First_Search	291	100.00
1654	Minimum Jumps to Reach Home	Medium	Array, Dynamic_Programming, Breadth_First_Search	192	100.00
0365	Water and Jug Problem	Medium	Math, Depth_First_Search, Breadth_First_Search	130	100.00

Day 12 Breadth First Search


0433	Minimum Genetic Mutation	Medium	String, Hash_Table, Breadth_First_Search	204	82.08
0752	Open the Lock	Medium	Array, String, Hash_Table, Breadth_First_Search	310	100.00
0127	Word Ladder	Hard	Top_Interview_Questions, String, Hash_Table, Breadth_First_Search	396	98.68

Day 13 Graph Theory


0997	Find the Town Judge	Easy	Array, Hash_Table, Graph	475	58.62
1557	Minimum Number of Vertices to Reach All Nodes	Medium	Graph	792	99.29

Day 14 Graph Theory


1615	Maximal Network Rank	Medium	Graph	282	100.00
0886	Possible Bipartition	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	397	100.00
0785	Is Graph Bipartite?	Medium	Depth_First_Search, Breadth_First_Search, Graph, Union_Find	215	82.35

0092 反转链表 II

fun reverseBetween(head: ListNode?, left: Int, right: Int): ListNode? {
         val xn = ListNode(-1)  // 链表
            xn.next = head

            var leftOld = xn
            for(i in 0 until left-1){
                leftOld = leftOld.next!!
            }

            var rightOld = leftOld
            for(i in 0 until right-left+1){
                rightOld = rightOld.next!!
            }
            
            var leftNew = leftOld.next
            var rightNew = rightOld.next
            
            leftOld.next = null
            rightOld.next = null
            
            reverseLinkedList(leftNew)
            
            leftOld.next = rightOld
            leftNew?.next = rightNew
            

            return xn.next
        }

        fun  reverseLinkedList(head:ListNode?){
            var prev: ListNode? = null
            var current = head
            while (current != null) {
                val next = current.next
                current.next = prev
                prev = current
                current = next
            }
        }

814 二叉树剪枝关键在根节点的删除，为了使得根结点可以和普通节点一样被删除，这里构造了一个新的根节点，在剪枝完成后在去掉这个新的根节点

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    fun pruneTree(root: TreeNode?): TreeNode? {
        var newRoot = TreeNode(1)
        newRoot.left = root
        explore(newRoot)
        var ans = newRoot.left
        newRoot.left = null
        return ans
    }
    fun explore(root: TreeNode?): TreeNode? {
        return root?.apply{
            explore(left)
            if(need(left)){
                left = null
            }
            explore(right)
            if(need(right)){
                right = null
            }
        }
    }
    fun need(t : TreeNode?):Boolean{
        return t?.run{
            if(`val` == 1){
                false
            }else{
                left == null && right == null
            }
        }?: false
    }
}

897 递增顺序搜索树

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    fun increasingBST(root: TreeNode): TreeNode? {
        val res: ArrayList<Int> = ArrayList()
        // 先对输入的二叉搜索树执行中序遍历，将结果保存到一个列表中；
        inOrder(root, res)

        // 然后对res操作，创建等价的只含有右节点的二叉搜索树，其过程等价于根据节点值创建一个链表。
        val dump = TreeNode(-1)
        var currenNode = dump
        res.forEach {
            currenNode.right = TreeNode(it)
            currenNode = currenNode.right!!
        }
        return dump.right
    }

    /**
     * 中序遍历  对输入的二叉搜索树执行中序遍历，将结果保存到一个列表中
     */
    fun inOrder(node: TreeNode?, res: ArrayList<Int>) {
        if (node == null) return
        inOrder(node.left, res)
        // 将node的值 加入到 res中
        res.add(node.`val`)
        inOrder(node.right, res)
    }
}

0166 分数到小数

fun fractionToDecimal(num: Int, den: Int): String {
//首先将负数全都转化为正数，这里需要用Long类型，不然-2^31直接转化为正数会爆Int
    val minus = 1L*num*den < 0
    val numerator = kotlin.math.abs(1L*num)
    val denominator = kotlin.math.abs(1L*den)
    var rmd = (numerator%denominator)
    val fore = (numerator/denominator).toString()
    if(rmd == 0L) {
        if(minus) {
            return "-$fore"
        }
        return fore
    } else {
        val mp = HashMap<Long, Int>(1000)
        var str = ""
        var ans = ""
        while(rmd != 0L) {
            rmd *= 10
            if(mp.containsKey(rmd)) {
                val loc = mp[rmd]!!
                ans = str.substring(0, loc) + '(' + str.substring(loc) + ')'
                break
            } else {
                mp[rmd] = str.length
                str += (rmd/denominator).toString()
                rmd %= denominator
            }
        }
        val tmp = if(ans == "") ("$fore.$str") else ("$fore.$ans")
        return if(minus) ("-$tmp") else (tmp)
    }
}

0919 二叉搜索树的插入

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class CBTInserter(val root: TreeNode?) {
    val queue = LinkedList<TreeNode>()
    init{
        // println(root)
       queue.offer(root!!) 
       while(!queue.isEmpty()){
           var it = queue.peek()
           if(it.right == null){
              break 
           }
           queue.poll()
           it.apply{
            //    println(`val`)
               left?.let{
                  queue.offer(it) 
               }
               right?.let{
                  queue.offer(it) 
               }
           }
       }
    }
    fun insert(v: Int): Int {
        var p = queue.peek()
        if(p.left == null){
           p.left = TreeNode(v)
        }else{
            p.right = TreeNode(v)
            queue.poll().apply{
                queue.offer(left!!)
                queue.offer(right!!)
            }
        }
        return p.`val`
    }

    fun get_root(): TreeNode? {
        return root
    }

}

/**
 * Your CBTInserter object will be instantiated and called as such:
 * var obj = CBTInserter(root)
 * var param_1 = obj.insert(v)
 * var param_2 = obj.get_root()
 */

814 二叉树剪枝

fun pruneTree(root: TreeNode?): TreeNode? {
        var newRoot = TreeNode(1)
        newRoot.left = root
        explore(newRoot)
        var ans = newRoot.left
        newRoot.left = null
        return ans
    }
    fun explore(root: TreeNode?): TreeNode? {
        return root?.apply{
            explore(left)
            if(need(left)){
                left = null
            }
            explore(right)
            if(need(right)){
                right = null
            }
        }
    }
    fun need(t : TreeNode?):Boolean{
        return t?.run{
            if(`val` == 1){
                false
            }else{
                left == null && right == null
            }
        }?: false
    }

二叉树的层平均值

License

kenken-xr/LeetCode-in-Kotlin

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