Leetcode 3. Longest Substring Without Repeating Characters(最长不重复子串)

Given 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.

Code：

class Solution {public:    int lengthOfLongestSubstring(string s) {        int m[256] = {0};//建表        int ans = 0;//保存结果        int begin = 0;//当年前字符串开始的位置        for(int i =0;i<s.size();i++){            if(m[s[i]] == 0||m[s[i]]<begin)//下一个字符没有出现过，或者begin有更新            {                ans = max(ans,i-begin+1);            }            else{//如果碰到重复的字符                //更新left                begin = m[s[i]];            }            m[s[i]] = i+1;        }        return ans;    }};