Difficulty-难度分类（简单、中等、困难）

难度是根据提交的代码通过率来得出的

Easy

LeetCode NO.	Title
1	Two Sum
7	Reverse Integer
9	Palindrome Number
13	Roman to Integer
14	Longest Common Prefix
20	Valid Parentheses
21	Merge Two Sorted Lists
26	Remove Duplicates from Sorted Array
27	Remove Element
28	Implement strStr()
35	Search Insert Position

Medium

LeetCode NO.	Title
2	Add Two Numbers
3	Longest Substring Without Repeating Characters
5	Longest Palindromic Substring
6	ZigZag Conversion
8	String to Integer (atoi)
11	Container With Most Water
12	Integer to Roman
15	3Sum
16	3Sum Closest
17	Letter Combinations of a Phone Number
18	4Sum
19	Remove Nth Node From End of List
22	Generate Parentheses
24	Swap Nodes in Pairs
31	Next Permutation
33	Search in Rotated Sorted Array
34	Search for a Range

Hard

LeetCode NO.	Title
4	Median of Two Sorted Arrays
23	Merge k Sorted Lists
25	Reverse Nodes in k-Group

Tags-数据结构分类

数据结构是指算法中处理的数据和借助其他数据结构完成算法用到的数据结构

Array

LeetCode NO.	Title
1	Two Sum
4	Median of Two Sorted Arrays
11	Container With Most Water
15	3Sum
16	3Sum Closest
18	4Sum
26	Remove Duplicates from Sorted Array
27	Remove Element
31	Next Permutation
33	Search in Rotated Sorted Array
34	Search for a Range
35	Search Insert Position

Dynamic Programming

String

LeetCode NO.	Title
3	Longest Substring Without Repeating Characters
5	Longest Palindromic Substring
6	ZigZag Conversion
8	String to Integer (atoi)
12	Integer to Roman
13	Roman to Integer
14	Longest Common Prefix
17	Letter Combinations of a Phone Number
20	Valid Parentheses
22	Generate Parentheses
28	Implement strStr()

Math

LeetCode NO.	Title
2	Add Two Numbers
7	Reverse Integer
8	String to Integer (atoi)
9	Palindrome Number
12	Integer to Roman
13	Roman to Integer

Tree

HashTable

LeetCode NO.	Title
1	Two Sum
3	Longest Substring Without Repeating Characters
18	4Sum

Depth-first Search

Binary Search

LeetCode NO.	Title
4	Median of Two Sorted Arrays
33	Search in Rotated Sorted Array
34	Search for a Range
35	Search Insert Position

Two Pointers

LeetCode NO.	Title
3	Longest Substring Without Repeating Characters
11	Container With Most Water
15	3Sum
16	3Sum Closest
18	4Sum
19	Remove Nth Node From End of List
26	Remove Duplicates from Sorted Array
27	Remove Element
28	Implement strStr()

Backtracking

LeetCode NO.	Title
17	Letter Combinations of a Phone Number
22	Generate Parentheses

Design

Breadth-first Search

Stack

LeetCode NO.	Title
20	Valid Parentheses

Bit Manipulation

Linked List

LeetCode NO.	Title
2	Add Two Numbers
19	Remove Nth Node From End of List
21	Merge Two Sorted Lists
23	Merge k Sorted Lists
24	Swap Nodes in Pairs
25	Reverse Nodes in k-Group

Greedy

Heap

LeetCode NO.	Title
23	Merge k Sorted Lists

Sort

Divide and Conquer

LeetCode NO.	Title
4	Median of Two Sorted Arrays
23	Merge k Sorted Lists

Graph

Trie

Binary Search Tree

Union Find

Segment Tree

Recursion

Binary Indexed Tree

Queue

Topological Sort

Minimax

Brainteaser

Reservoir Sampling

Geometry

Map

Memoization