Solutions for LeetCode algorithm problems, continually updating.

ID	Title && solution	Coefficient of difficulty	remarks
0001	Two Sum	Easy	array; lookup table
0002	Add Two Numbers	Medium	linked list
0003	Longest Substring Without Repeating Characters	Medium	sliding window
0004	4. Median of Two Sorted Arrays	Hard	binary search
0007	7. Reverse Integer	Easy	math
0009	9. Palindrome Number	Easy	math
0011	11. Container With Most Water	Medium	array; double index
0013	13. Roman to Integer	Easy	math
0014	14. Longest Common Prefix	Easy
0015	15. 3Sum	Medium
0017	Letter Combinations of a Phone Number	Medium	tree
0019	19. Remove Nth Node From End of List	Medium	linked list
0020	Valid Parentheses	Easy	string; stack
0021	Merge Two Sorted Lists	Easy	linked list
0023	23. Merge k Sorted Lists	Hard	linked list; heap
0024	24. Swap Nodes in Pairs	Medium	linked list
0025	Reverse Nodes in k-Group	Hard	linked list
0026	Remove Duplicates from Sorted Array	Easy	array; double index
0027	Remove Element	Easy	array
0028	28. Implement strStr()	Easy	double index
0033	Search in Rotated Sorted Array	Medium	binary search
0034	Find First and Last Position of Element in Sorted Array	Medium	binary search
0035	35. Search Insert Position	Easy	binary search
0048	48. Rotate Image	Medium	array
0053	53. Maximum Subarray	Easy	dynamic programming
0058	58. Length of Last Word	Easy
0061	Rotate List	Medium	linked list
0062	Unique Paths	Medium	recursion; memory search; dynamic programming
0063	Unique Paths 2	Medium	recursion; memory search; dynamic programming
0064	Minimum Path Sum	Medium	dynamic programming; dfs
0066	66. Plus One	Easy	math
0067	add Binary	Easy
0069	Sqrt(x)	Easy	binary search
0070	Climbing Stairs	Easy	dynamic programming
0075	75. Sort Colors	Medium	sort
0076	Minimum Window Substring	Hard	sliding window
0077	77. Combinations	Medium	backtracking; combine
0079	79. Word Search	Medium	backtracking; array
0080	80. Remove Duplicates from Sorted Array II	Medium	double index
0082	82. Remove Duplicates from Sorted List II	Medium	linked list
0083	83. Remove Duplicates from Sorted List	Easy	linked list
0086	86. Partition List	Medium	linked list
0088	88. Merge Sorted Array	Easy	sort
0092	92. Reverse Linked List II	Medium	linked list
0094	Binary Tree Inorder Traversal	Medium	binary tree
0100	Same Tree	Easy	binary tree
0101	Symmetric Tree	Easy	stack; recursion; iterative
0102	102. Binary Tree Level Order Traversal	Medium	binary tree; bfs
0104	104. Maximum Depth of Binary Tree	Easy	binary tree
0107	Binary Tree Level Order Traversal II	Easy	binary tree
0111	Minimum Depth of Binary Tree	Easy	binary tree
0112	Path Sum	Easy	binary tree
0120	Triangle	Medium	dynamic programming; dfs
0121	121. Best Time to Buy and Sell Stock	Easy
0122	122. Best Time to Buy and Sell Stock II	Easy	greedy
0125	Valid Palindrome	Easy
0136	136. Single Number	Easy	hash table; bit manipulation
0144	144. Binary Tree Preorder Traversal	Medium	binary tree
0148	148. Sort List	Medium	sort; linked list
0150	150. Evaluate Reverse Polish Notation	Medium	stack
0153	153. Find Minimum in Rotated Sorted Array	Medium	binary search
0155	155. Min Stack	Easy	stack
0165	165. Compare Version Numbers	Medium	string
0167	Two Sum II - Input array is sorted	Easy	对撞指针(双索引)
0179	179. Largest Number	Medium	sort
0198	House Robber	Easy	memory search; dynamic programming
0200	200. Number of Islands	Medium	dfs; bfs
0203	203. Remove Linked List Elements	Easy	linked list
0206	206. Reverse Linked List	Easy	linked list
0208	208. Implement Trie (Prefix Tree)	Medium	trie
0209	Minimum Size Subarray Sum	Medium	sliding window
0211	211. Add and Search Word - Data structure design	Medium	trie
0215	215. Kth Largest Element in an Array	Medium	sort
0217	217. Contains Duplicate	Easy	map
0219	219. Contains Duplicate II	Easy	map
0226	Invert Binary Tree	Easy	recursion; binary tree
0235	235. Lowest Common Ancestor of a Binary Search Tree	Easy	recursion; binary tree
0236	236. Lowest Common Ancestor of a Binary Tree	Medium	recursion; binary tree
0237	237. Delete Node in a Linked List	Easy	linked list
0257	257. Binary Tree Paths	Easy	binary tree
0258	258. Add Digits	Easy	math
0283	Move Zeroes(solution1) Move Zeroes(solution2)	Easy	array
0300	Longest Increasing Subsequence	Medium	dp
0303	303. Range Sum Query - Immutable	Easy
0304	304. Range Sum Query 2D - Immutable	Medium	dp
0307	307. Range Sum Query - Mutable	Medium	segment tree
0328	328. Odd Even Linked List	Medium	singly linked list
0343	Integer Break	Medium	recursion; memory search; dynamic programming
0344	344. Reverse String	Easy	double index
0345	345. Reverse Vowels of a String	Easy	double index
0347	347. Top K Frequent Elements	Medium	map; heap; array
0349	Intersection of Two Arrays	Easy	set
0350	Intersection of Two Arrays II	Easy	map
0376	Wiggle Subsequence	Medium	dp
0392	Is Subsequence	Medium	greedy algorithm
0404	404. Sum of Left Leaves	Easy	binary tree
0416	Partition Equal Subset Sum	Medium	dp; 0-1 knapsack problem
0435	Non-overlapping Intervals(dp solution) Non-overlapping Intervals(greedy solution)	Medium	dp; 0-1 knapsack problem
0437	437. Path Sum III	Easy	binary tree
0438	Find All Anagrams in a String	Easy	sliding window
0447	Number of Boomerangs	Easy
0454	4Sum II	Medium
0455	Assign Cookies	Easy	greedy algorithm
0557	557. Reverse Words in a String III	Easy	string
0674	674. Longest Continuous Increasing Subsequence	Easy
0677	677. Map Sum Pairs	Medium	trie
0704	Binary Search	Easy	binary search
0713	713. Subarray Product Less Than K	Medium	sliding window
0717	717. 1-bit and 2-bit Characters	Easy
0728	Self Dividing Numbers	Easy
0735	735. Asteroid Collision	Medium	stack
0747	Largest Number At Least Twice of Others	Easy
0872	872. Leaf-Similar Trees	Easy	binary tree
1021	1021. Remove Outermost Parentheses	Easy	stack