LeetCode 问题难度，面试出现频率及问题相关数据结构和算法


1	Two Sum	2	5	array	sort
				set	Two Pointers
2	Add Two Numbers	3	4	linked list	Two Pointers
					Math
3	Longest Substring Without Repeating Characters	3	2	string	Two Pointers
				hashtable
4	Median of Two Sorted Arrays	5	3	array	Binary Search
5	Longest Palindromic Substring	4	2	string
6	ZigZag Conversion	3	1	string
7	Reverse Integer	2	3		Math
8	String to Integer (atoi)	2	5	string	Math
9	Palindrome Number	2	2		Math
10	Regular Expression Matching	5	3	string	Recursion
					DP
11	Container With Most Water	3	2	array	Two Pointers
12	Integer to Roman	3	4		Math
13	Roman to Integer	2	4		Math
14	Longest Common Prefix	2	1	string
15	3Sum	3	5	array	Two Pointers
16	3Sum Closest	3	1	array	Two Pointers
17	Letter Combinations of a Phone Number	3	3	string	DFS
18	4Sum	3	2	array
19	Remove Nth Node From End of List	2	3	linked list	Two Pointers
20	Valid Parentheses	2	5	string	Stack
21	Merge Two Sorted Lists	2	5	linked list	sort
					Two Pointers
					merge
22	Generate Parentheses	3	4	string	DFS
23	Merge k Sorted Lists	3	4	linked list	sort
				heap	Two Pointers
					merge
24	Swap Nodes in Pairs	2	4	linked list
25	Reverse Nodes in k-Group	4	2	linked list	Recursion
					Two Pointers
26	Remove Duplicates from Sorted Array	1	3	array	Two Pointers
27	Remove Element	1	4	array	Two Pointers
28	Implement strStr()	4	5	string	Two Pointers
					KMP
					rolling hash
29	Divide Two Integers	4	3		Binary Search
					Math
30	Substring with Concatenation of All Words	3	1	string	Two Pointers
31	Next Permutation	5	2	array	permutation
32	Longest Valid Parentheses	4	1	string	DP
33	Search in Rotated Sorted Array	4	3	array	Binary Search
34	Search for a Range	4	3	array	Binary Search
35	Search Insert Position	2	2	array
36	Valid Sudoku	2	2	array
37	Sudoku Solver	4	2	array	DFS
38	Count and Say	2	2	string	Two Pointers
39	Combination Sum	3	3	array	combination
40	Combination Sum II	4	2	array	combination
41	First Missing Positive	5	2	array	sort
42	Trapping Rain Water	4	2	array	Two Pointers
					Stack
43	Multiply Strings	4	3	string	Two Pointers
					Math
44	Wildcard Matching	5	3	string	Recursion
					DP
					greedy
45	Jump Game II	4	2	array
46	Permutations	3	4	array	permutation
47	Permutations II	4	2	array	permutation
48	Rotate Image	4	2	array
49	Anagrams	3	4	string
				hashtable
50	Pow(x, n)	3	5		Binary Search
					Math
51	N-Queens	4	3	array	DFS
52	N-Queens II	4	3	array	DFS
53	Maximum Subarray	3	3	array	DP
54	Spiral Matrix	4	2	array
55	Jump Game	3	2	array
56	Merge Intervals	4	5	array	sort
				linked list	merge
				red-black tree
57	Insert Interval	4	5	array	sort
				linked list	merge
				red-black tree
58	Length of Last Word	1	1	string
59	Spiral Matrix II	3	2	array
60	Permutation Sequence	5	1		permutation
					Math
61	Rotate List	3	2	linked list	Two Pointers
62	Unique Paths	2	3	array	DP
63	Unique Paths II	3	3	array	DP
64	Minimum Path Sum	3	3	array	DP
65	Valid Number	2	5	string	Math
66	Plus One	1	2	array	Math
67	Add Binary	2	4	string	Two Pointers
					Math
68	Text Justification	4	2	string
69	Sqrt(x)	4	4		Binary Search
70	Climbing Stairs	2	5		DP
71	Simplify Path	3	1	string	Stack
72	Edit Distance	4	3	string	DP
73	Set Matrix Zeroes	3	5	array
74	Search a 2D Matrix	3	3	array	Binary Search
75	Sort Colors	4	2	array	sort
					Two Pointers
76	Minimum Window Substring	4	2	string	Two Pointers
77	Combinations	3	4		combination
78	Subsets	3	4	array	Recursion
					combination
79	Word Search	3	4	array	DFS
80	Remove Duplicates from Sorted Array II	2	2	array	Two Pointers
81	Search in Rotated Sorted Array II	5	3	array	Binary Search
82	Remove Duplicates from Sorted List II	3	3	linked list	Recursion
					Two Pointers
83	Remove Duplicates from Sorted List	1	3	linked list
84	Largest Rectangle in Histogram	5	2	array	Stack
85	Maximal Rectangle	5	1	array	DP
					Stack
86	Partition List	3	3	linked list	Two Pointers
87	Scramble String	5	2	string	Recursion
					DP
88	Merge Sorted Array	2	5	array	Two Pointers
					merge
89	Gray Code	4	2		combination
90	Subsets II	4	2	array	Recursion
					combination
91	Decode Ways	3	4	string	Recursion
					DP
92	Reverse Linked List II	3	2	linked list	Two Pointers
93	Restore IP Addresses	3	3	string	DFS
94	Binary Tree Inorder Traversal	4	3	tree	Recursion
				hashtable	morris
					Stack
95	Unique Binary Search Trees II	4	1	tree	DP
					DFS
96	Unique Binary Search Trees	3	1	tree	DP
97	Interleaving String	5	2	string	Recursion
					DP
98	Validate Binary Search Tree	3	5	tree	DFS
99	Recover Binary Search Tree	4	2	tree	DFS
100	Same Tree	1	1	tree	DFS
101	Symmetric Tree	1	2	tree	DFS
102	Binary Tree Level Order Traversal	3	4	tree	BFS
103	Binary Tree Zigzag Level Order Traversal	4	3	queue	BFS
				tree	Stack
104	Maximum Depth of Binary Tree	1	1	tree	DFS
105	Construct Binary Tree from Preorder and Inorder Tr	3	3	array	DFS
				tree
106	Construct Binary Tree from Inorder and Postorder T	3	3	array	DFS
				tree
107	Binary Tree Level Order Traversal II	3	1	tree	BFS
108	Convert Sorted Array to Binary Search Tree	2	3	tree	DFS
109	Convert Sorted List to Binary Search Tree	4	3	linked list	Recursion
					Two Pointers
110	Balanced Binary Tree	1	2	tree	DFS
111	Minimum Depth of Binary Tree	1	1	tree	DFS
112	Path Sum	1	3	tree	DFS
113	Path Sum II	2	2	tree	DFS
114	Flatten Binary Tree to Linked List	3	3	tree	Recursion
					Stack
115	Distinct Subsequences	4	2	string	DP
116	Populating Next Right Pointers in Each Node	3	3	tree	DFS
117	Populating Next Right Pointers in Each Node II	4	2	tree	DFS
118	Pascal's Triangle	2	1	array
119	Pascal's Triangle II	2	1	array
120	Triangle	3	1	array	DP
121	Best Time to Buy and Sell Stock	2	1	array	DP
122	Best Time to Buy and Sell Stock II	3	1	array	greedy
123	Best Time to Buy and Sell Stock III	4	1	array	DP
124	Binary Tree Maximum Path Sum	4	2	tree	DFS
125	Valid Palindrome	2	5	string	Two Pointers
126	Word Ladder II	1	1
127	Word Ladder	3	5	graph	BFS
					shortest path
128	Longest Consecutive Sequence	4	3	array
129	Sum Root to Leaf Numbers	2	4	tree	DFS
130	Surrounded Regions	4	3	array	BFS
					DFS
131	Palindrome Partitioning	3	4	string	DFS
132	Palindrome Partitioning II	4	3	string	DP