leetcode 3 Longest Substring Without Repeating Characters

solution:

 1 class Solution {
 2 public:
 3     int lengthOfLongestSubstring(string s) {
 4       std::vector<bool> v(256, false);
 5       int len = s.length();
 6       int l=0, ans=0;
 7       for (int i = 0; i < len; ++i) {
 8         int tmp = s[i]-0x0;
 9         if (v[tmp] == true) {
10           ans = std::max(ans, i-l);
11           while (l < i) {
12             if (s[l] == s[i]) {
13               ++l;
14               break;
15             } else {
16               v[s[l]-0x0] = false;
17             }
18             ++l;
19           }
20         } else {
21           v[tmp] = true;
22         }
23       }
24       ans = std::max(ans, len-l);
25       return ans;
26     }
27 };

需要注意这里的字符不仅仅是英文字母，字符char不多于256个，数组范围设
为256即可。O(n)的扫描字符串，每遇到相同的，比对max。