Longest Substring Without Repeating Characters 7 lines with c++ in 12ms

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4         int len = s.length(), m = 0, l = 0, p[256] = { 0 };
 5         for(int i = 0; i < len; ) {
 6             l = max(l, p[s.at(i)]);
 7             p[s.at(i)] = ++i;
 8             m = max(m, i - l);
 9         }
10         return m;
11     }
12 };