Algorithm Solutions

Leetcode Solutions

#	Title	Difficulty	Blog	Others
1	Two Sum	Easy	Two Sum
2	Add Two Numbers	Medium	Add Two Numbers
3	Longest Substring Without Repeating Characters	Medium	Longest Substring Without Repeating Characters
4	Median of Two Sorted Arrays	Hard	Median of Two Sorted Arrays	Binary Search *
5	Longest Palindromic Substring	Medium	Longest Palindromic Substring	dp & Manacher’s Algorithm *
6	ZigZag Conversion	Medium	ZigZag Conversion
7	Reverse Integer	Easy	Reverse Integer
8	String to Integer (atoi)	Medium	String to Integer (atoi)
9	Palindrome Number	Easy	Palindrome Number
10	Regular Expression Matching	Hard	Regular Expression Matching	dp **
11	Container With Most Water	Medium	Container With Most Water
12	Integer to Roman	Medium	Integer to Roman
13	Roman to Integer	Easy	Roman to Integer
14	Longest Common Prefix	Easy	Longest Common Prefix
15	3Sum	Medium	3Sum
16	3Sum Closest	Medium	3Sum Closest
17	Letter Combinations of a Phone Number	Medium	Letter Combinations of a Phone Number
18	4Sum	Medium	4Sum
19	Remove Nth Node From End of List	Medium	Remove Nth Node From End of List
20	Valid Parentheses	Easy	Valid Parentheses
21	Merge Two Sorted Lists	Easy	Merge Two Sorted Lists
22	Generate Parentheses	Medium	Generate Parentheses
23	Merge k Sorted Lists	Hard	Merge k Sorted Lists	Divide Conquer & Heap Sort
24	Swap Nodes in Pairs	Medium	Swap Nodes in Pairs
25	Reverse Nodes in k-Group	Hard	Reverse Nodes in k-Group	Reverse List
26	Remove Duplicates from Sorted Array	Easy	Remove Duplicates from Sorted Array
27	Remove Element	Easy	Remove Element
28	Implement strStr()	Easy	Implement strStr()	KMP Algorithm *
29	Divide Two Integers	Medium	Divide Two Integers
30	Substring with Concatenation of All Words	Hard	Substring with Concatenation of All Words
31	Next Permutation	Medium	Next Permutation
32	Longest Valid Parentheses	Hard	Longest Valid Parentheses	DP/Stack *
33	Search in Rotated Sorted Array	Medium	Search in Rotated Sorted Array
34	Find First and Last Position of Element in Sorted Array	Medium	Find First and Last Position of Element in Sorted Array
35	Search Insert Position	Easy	Search Insert Position
36	Valid Sudoku	Medium	Valid Sudoku
37	Sudoku Solver	Hard	Sudoku Solver	Backtracking *
38	Count And Say	Easy	Count And Say
39	Combination Sum	Medium	Combination Sum	backtracing
40	Combination Sum II	Medium	Combination Sum II	backtracing
41	First Missing Positive	Hard	First Missing Positive	Trick method
42	Trapping Rain Water	Hard	Trapping Rain Water	Dp/Stack/Two Pointer
43	Multiply Strings	Medium	Multiply Strings
44	Wildcard Matching	Hard	Wildcard Matching	DP*
45	Jump Game II	Hard	Jump Game II
46	Permutations	Medium	Permutations
47	Permutations II	Medium	Permutations II
48	Rotate Image	Medium	Rotate Image
49	Group Anagrams	Medium	Group Anagrams
50	Pow(x, n)	Medium	Pow(x, n)
53	Maximum Subarray	Easy	Maximum Subarray	Kadane Algorithm *
56	Merge Intervals	Medium	Merge Intervals
57	Insert Interval	Hard	Insert Interval
58	Length of Last Word	Easy	Length of Last Word
66	Plus One	Easy	Plus One
67	Add Binary	Easy	Add Binary
69	Sqrt(x)	Easy	Sqrt(x)
70	Climbing Stairs	Easy	Climbing Stairs
71	Simplify Path	Medium	Simplify Path	dp
72	Edit Distance	Hard	Edit Distance
77	Combinations	Medium	Combinations	backtracing
83	Remove Duplicates from Sorted List	Easy	Remove Duplicates from Sorted List
88	Merge Sorted Array	Easy	Merge Sorted Array
94	Binary Tree Inorder Traversal	Medium	Binary Tree Inorder Traversal
100	Same Tree	Easy	Same Tree
101	Symmetric Tree	Easy	Symmetric Tree	* Binary-Tree Traverse
102	Binary Tree Level Order Traversal	Medium	Binary Tree Level Order Traversal	* Binary-Tree Traverse
104	Maximum Depth of Binary Tree	Easy	Maximum Depth of Binary Tree	* Binary-Tree Traverse
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Construct Binary Tree from Preorder and Inorder Traversal
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	Construct Binary Tree from Inorder and Postorder Traversal
107	Binary Tree Level Order Traversal II	Easy	Binary Tree Level Order Traversal II	* Binary-Tree Traverse
108	Convert Sorted Array to Binary Search Tree	Easy	Convert Sorted Array to Binary Search Tree	* Binary-Tree Traverse
112	Path Sum	Easy	Path Sum
113	Path Sum II	Medium	Path Sum II
121	Best Time to Buy and Sell Stock	Easy	Best Time to Buy and Sell Stock
122	Best Time to Buy and Sell Stock	Easy	Best Time to Buy and Sell Stock
123	Best Time to Buy and Sell Stock III	Hard	Best Time to Buy and Sell Stock III	dp
144	Binary Tree Preorder Traversal	Medium	Binary Tree Preorder Traversal
145	Binary Tree Postorder Traversal	Hard	Binary Tree Postorder Traversal
188	Best Time to Buy and Sell Stock IV	Hard	Best Time to Buy and Sell Stock IV	dp
198	House Robber	Easy	House Robber	dp
213	House Robber II	Easy	House Robber II	dp
216	Combination Sum III	Medium	Combination Sum III	backtracing
236	Lowest Common Ancestor of a Binary Tree	Medium	Lowest Common Ancestor of a Binary Tree
279	Perfect Squares	Medium	Perfect Squares	dp
287	Find the Duplicate Number	Medium	Find the Duplicate Number	fast-slow-pointer
300	Longest Increasing Subsequence	Medium	Longest Increasing Subsequence	dp
309	Best Time to Buy and Sell Stock with Cooldown	Medium	Best Time to Buy and Sell Stock with Cooldown	dp
337	House Robber III	Medium	House Robber III	dp
373	Find K Pairs with Smallest Sums	Medium	Find K Pairs with Smallest Sums
377	Combination Sum IV	Medium	Combination Sum IV	dp
378	Kth Smallest Element in a Sorted Matrix	Medium	Kth Smallest Element in a Sorted Matrix
407	Trapping Rain Water II	Hard	Trapping Rain Water II
437	Path Sum III	Easy	Path Sum III
442	Find All Duplicates in an Array	Medium	Find All Duplicates in an Array
448	Find All Numbers Disappeared in an Array	Easy	Find All Numbers Disappeared in an Array
468	Validate IP Address	Medium	Validate IP Address
538	Convert BST to Greater Tree	Easy	Convert BST to Greater Tree
583	Delete Operation for Two Strings	Medium	Delete Operation for Two Strings	dp
645	Set Mismatch	Easy	Set Mismatch
650	2 Keys Keyboard	Medium	2 Keys Keyboard	dp
669	Trim a Binary Search Tree	Easy	Trim a Binary Search Tree
671	Second Minimum Node In a Binary Tree	Easy	Second Minimum Node In a Binary Tree
687	Longest Univalue Path	Easy	Longest Univalue Path
714	Best Time to Buy and Sell Stock with Transaction Fee	Medium	Best Time to Buy and Sell Stock with Transaction Fee	dp
873	Length of Longest Fibonacci Subsequence	Medium	Length of Longest Fibonacci Subsequence	dp
953	Verifying an Alien Dictionary	Easy	Verifying an Alien Dictionary
1027	Longest Arithmetic Sequence	Medium	Longest Arithmetic Sequence	dp

剑指 offer

#	Title	Blog	Category
3	二维数组中的查找	二维数组中的查找	数组、查找
4	替换空格	替换空格	字符串
5	从尾到头打印链表	从尾到头打印链表	链表
6	重建二叉树	重建二叉树	树 *
7	用两个栈实现队列	用两个栈实现队列	栈、队列
8	旋转数组的最小数字	旋转数组的最小数字	查找和排序
9	斐波那契数列	斐波那契数列	递归和循环
9_1	跳台阶	跳台阶	递归和循环
9_2	变态跳台阶	变态跳台阶	递归和循环
9_3	矩形覆盖	矩形覆盖	递归和循环
10	二进制中 1 的个数	二进制中 1 的个数	位运算
11	数值的整数次方	数值的整数次方	代码的完整性
14	调整数组顺序使奇数位于偶数前面	调整数组顺序使奇数位于偶数前面	代码的完整性、数组
15	链表中倒数第 k 个结点	链表中倒数第 k 个结点	代码的鲁棒性、链表
16	反转链表	反转链表	代码的鲁棒性、链表
17	合并两个排序的链表	合并两个排序的链表	代码的鲁棒性、链表
18	树的子结构	树的子结构	代码的鲁棒性
19	二叉树的镜像	二叉树的镜像	面试思路
20	顺时针打印矩阵	顺时针打印矩阵	画图让抽象形象化、数组
21	包含 min 函数的栈	包含 min 函数的栈	举例让抽象形象化、栈
22	栈的压入、弹出序列	栈的压入、弹出序列	举例让抽象形象化、栈
23	从上往下打印二叉树	从上往下打印二叉树	举例让抽象形象化
24	二叉搜索树的后序遍历序列	二叉搜索树的后序遍历序列	举例让抽象形象化
25	二叉树中和为某一值的路径	二叉树中和为某一值的路径	举例让抽象形象化
26	复杂链表的复制	复杂链表的复制	分解让复杂问题简单
27	二叉搜索树与双向链表	二叉搜索树与双向链表	分解让复杂问题简单*
28	字符串的排列	字符串的排列	分解让复杂问题简单*
31	连续子数组的最大和	连续子数组的最大和	时间效率、数组
32	整数中 1 出现的次数	整数中 1 出现的次数	时间效率
33	把数组排成最小的数	把数组排成最小的数	时间效率、数组 *
34	丑数	丑数	时间空间效率的平衡、数组
35	第一个只出现一次的字符	第一个只出现一次的字符	时间空间效率的平衡、字符串
36	数组中的逆序对	数组中的逆序对	时间空间效率的平衡、数组
37	两个链表的第一个公共结点	两个链表的第一个公共结点	时间空间效率的平衡、链表
38	数字在排序数组中出现的次数	数字在排序数组中出现的次数	知识迁移能力、数组
39	二叉树的深度	二叉树的深度	知识迁移能力、数组
39_2	平衡二叉树	平衡二叉树	知识迁移能力
40	数组中只出现一次的数字	数组中只出现一次的数字	知识迁移能力、数组
41	和为 S 的两个数字	和为 S 的两个数字	知识迁移能力
41_2	和为 S 的连续正数序列	和为 S 的连续正数序列	知识迁移能力
42	翻转单词顺序列	翻转单词顺序列	知识迁移能力、字符串
42_2	左旋转字符串	左旋转字符串	知识迁移能力、字符串
44	扑克牌顺子	扑克牌顺子	抽象建模能力
45	圆圈中最后剩下的数	圆圈中最后剩下的数	抽象建模能力、模拟
46	求 1+2+3+…+n	求 1+2+3+…+n	发散思维能力
47	不用加减乘除做加法	不用加减乘除做加法	发散思维能力
49	把字符串转换成整数	把字符串转换成整数	综合、字符串
51	数组中重复的数字	数组中重复的数字	数组
52	构建乘积数组	构建乘积数组	数组
53	正则表达式匹配	正则表达式匹配	字符串
54	表示数值的字符串	表示数值的字符串	字符串
55	字符流中第一个不重复的字符	字符流中第一个不重复的字符	字符串
56	链表中环的入口结点	链表中环的入口结点	链表
57	删除链表中重复的结点	删除链表中重复的结点	链表
58	二叉树的下一个结点	二叉树的下一个结点	树
59	对称的二叉树	对称的二叉树	树*
60	把二叉树打印成多行	把二叉树打印成多行	树
61	按之字形顺序打印二叉树	按之字形顺序打印二叉树	树
62	序列化二叉树	序列化二叉树	树
63	二叉搜索树的第 k 个结点	二叉搜索树的第 k 个结点	树
64	数据流中的中位数	数据流中的中位数	树*
65	滑动窗口的最大值	滑动窗口的最大值	栈和队列*
66	矩阵中的路径	矩阵中的路径	回溯法
67	机器人的运动范围	机器人的运动范围	回溯法

专题

#	Title	Category
1	二叉树相关知识点总结	树
2	LeetCode 题目专题	LeetCode