LeetCode Statistics

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	ID	Question	Diff	Freq	Data Structure	Algorithms
	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

Dynamic Programming

Edit Distance Maximum Subarray Minimum Path Sum Unique Paths Unique Paths II Longest Palindromic Substring Interleaving String Triangle Distinct Subsequences Decode Ways Palindrome Partitioning II Maximal Rectangle

Recursion

N-Queens N-Queens II Balanced Binary Tree Binary Tree Inorder Traversal Binary Tree Maximum Path Sum Convert Sorted Array to Binary Search Tree Convert Sorted List to Binary Search Tree Flatten Binary Tree to Linked List Maximum Depth of Binary Tree Minimum Depth of Binary Tree Path Sum Permutations Permutations II Populating Next Right Pointers in Each Node Pow(x, n) Same Tree Subsets Sum Root to Leaf Numbers Swap Nodes in Pairs Symmetric Tree Valid Palindrome Validate Binary Search Tree Restore IP Addresses Combinations Interleaving String (dp is the best) Combination Sum II Letter Combinations of a Phone Numbers Word Search Construct Binary Tree from Inorder and Postorder Traversal Construct Binary Tree from Preorder and Inorder Traversal Generate Parentheses Surrounded Regions (runtime error) Palindrome Partitioning Combination Sum Sudoku Solver Unique Binary Search Trees II

Binary Search

Search Insert Position Search a 2D Matrix Search for a Range Search in Rotated Sorted Array Sqrt(x)

Sequence

Container With Most Water Count and Say First Missing Positive Implement strStr() Jump Game Jump Game II Length of Last Word Longest Common Prefix Longest Substring Without Repeating Characters Merge Sorted Array Palindrome Number Plus One Remove Duplicates from Sorted Array Remove Duplicates from Sorted Array II Remove Element Reverse Integer Search in Rotated Sorted Array II Sort Colors Two Sum 3Sum 3Sum Closest 4Sum Add Binary Longest Palindromic Substring Next Permutation Longest Valid Parentheses Climbing Stairs Permutation Sequence Simplify Path String to Integer (atoi) Minimum Window Substring Longest Consecutive Sequence Trapping Rain Water Valid Number

Linked List

Add Two Numbers Convert Sorted List to Binary Search Tree Merge Two Sorted Lists Partition List Remove Duplicates from Sorted List Remove Duplicates from Sorted List II Remove Nth Node From End of List Reverse Linked List II Reverse Nodes in k-Group Rotate List Swap Nodes in Pairs

Stack

Binary Tree Inorder Traversal Binary Tree Level Order Traversal II Valid Parentheses

Queue

Binary Tree Level Order Traversal Binary Tree Level Order Traversal II Populating Next Right Pointers in Each Node II Symmetric Tree Surrounded Regions Word Ladder

Tree

Balanced Binary Tree Binary Tree Inorder Traversal Binary Tree Level Order Traversal Binary Tree Level Order Traversal II Binary Tree Maximum Path Sum Convert Sorted Array to Binary Search Tree Convert Sorted List to Binary Search Tree Flatten Binary Tree to Linked List Maximum Depth of Binary Tree Minimum Depth of Binary Tree Path Sum Same Tree Sum Root to Leaf Numbers Symmetric Tree Validate Binary Search Tree

from http://blog.csdn.net/doc_sgl/article/details/11664539