Leetcode题解

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.

用一个哈希表存储访问过的字符，因为此处情况就是ascii字母表，用一个256的数组存储即可。每访问过一个字母，对应索引值加一，以此寻找最长非重复子串。

class Solution {public:    int lengthOfLongestSubstring(string s) {        vector<int> idx(256,-1);        int maxlen=0,m=0;        for(int  i=0;i<s.size();i++){            m=max(idx[s[i]]+1,m);            idx[s[i]]=i;            maxlen=max(maxlen,i-m+1);        }        return maxlen;    }};