leetcode 3 Longest Substring Without Repeating Characters

solution:

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
      std::vector<bool> v(256, false);
      int len = s.length();
      int l=0, ans=0;
      for (int i = 0; i < len; ++i) {
        int tmp = s[i]-0x0;
        if (v[tmp] == true) {
          ans = std::max(ans, i-l);
          while (l < i) {
            if (s[l] == s[i]) {
              ++l;
              break;
            } else {
              v[s[l]-0x0] = false;
            }
            ++l;
          }
        } else {
          v[tmp] = true;
        }
      }
      ans = std::max(ans, len-l);
      return ans;
    }
};

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。