Longest Substring Without Repeating Characters

class Solution {public:    int lengthOfLongestSubstring(string s) {        int dic[256];        for(int i = 0; i < 256; i++) dic[i] = -1;        int maxlen = 0, j = 0;        for(int i = 0; i < s.length(); i++){            if(dic[s[i]] == -1 || dic[s[i]] < j){                int len = i - j + 1;                maxlen = maxlen > len? maxlen: len;            }else{                j = dic[s[i]] + 1;            }            dic[s[i]] = i;        }        return maxlen;    }};