003.Longest Substring Without Repeating Characters

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4         const int ASCII_MAX = 256;
 5         int last[ASCII_MAX];
 6         memset(last, -1, sizeof(last));
 7         int startPos = 0; int len = 0;
 8         for (int i = 0; i < s.size(); ++i) {
 9             if (last[s[i]] >= startPos) {
10                 len = max(len, i - startPos);
11                 startPos = last[s[i]] + 1;
12             }
13             last[s[i]] = i;
14         }
15         return max(len, static_cast<int>(s.size()) - startPos);
16     }
17 };