LeetCode——003

/*///////////////////////////////////////////////////////////////////////////3. Longest Substring Without Repeating Characters My Submissions QuestionEditorial SolutionTotal Accepted: 141845 Total Submissions: 649486 Difficulty: MediumGiven a string, find the length of the longest substring without repeating characters.Examples:Given "abcabcbb", the answer is "abc", which the length is 3.Given "bbbbb", the answer is "b", with the length of 1.Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.Subscribe to see which companies asked this question////////////////////////////////////////////////////////////////////////*///思路：/* 用hashmap存放已经遍历的字符以及其位置，利用左右两个游标left & i ， 当i所指当前字符未曾遍历过则将其插入到map中，如果之前遍历过：又可以更新当前字符的位置为i，二是遍历过的位置在left或left之后，那么首先将left移动到上一次出现位置的下一个位置，然后更新map中当前的字符的位置为i。 最后判断一下len 与 i-letf+1 的大小取一个较大值。*/class Solution {public:    int lengthOfLongestSubstring(string s) {        //最长无重复子串        map<char,int> _mp;        if(s.size()==0)return 0;        int left=0;        int len=INT_MIN;        for(int i=0;i<s.size();i++){            if(_mp.find(s[i])==_mp.end()){                _mp[s[i]]=i;            }else{                if(left>_mp[s[i]]){                    _mp[s[i]]=i;                }else{                    left=_mp[s[i]]+1;                    _mp[s[i]]=i;                }            }         len=max(len,i-left+1);        }        return len;    }};