Leetcode打卡贴

Valid Number
Decode and Encode String
Summary Ranges

Merge Interval
String to Integer
One Edit Distance

Insert interval 和merge interval一类，先加到list里面,之后merge

加油楼主

Range Sum Query - immutable 前缀和数组
Range Sum Query - mutable 前缀和数组过了，其实是用线段树，哪天需要看一下
Evaluate Reverse Polish Notation 栈，遇到数字入栈，遇到符号出，计算之后再入栈，判断给的字符串是数字还是符号自己有个bug
Strobogrammatic Number

Word Abbreviation
convert BST to Greater Tree

Find Celebrity
Insert Delete GetRandom O(1) 很巧妙两道题

Repeated DNA
Valid Sudoku
Group Anagram

Number of Connected Components in an undirected Graph
Graph Valid Tree
Number of Island
三道都是纯BFS 改天试一下用Union Find

Surrounded regions 建议从边上O区域，之后标记成另外一个字母，比找O然后检查是否在边界简单些