1 class Solution { 2 public: 3     string minWindow(string s, string t) { 4         int m = s.length(), n = t.length(); 5         if (!m || !n) return ""; 6         int times[128] = {
   0}; 7         bool exist[128] = {
   false}; 8         for (int i = 0; i < n; i++) { 9             times[t[i]]++;10             exist[t[i]] = true;11         }12         int l = 0, r = -1, idx = 0, len = INT_MAX;13         while (l < m && r < m) {14             if (n) {15                 times[s[++r]]--;16                 if (exist[s[r]] && times[s[r]] >= 0) n--;17             }18             else {19                 if (len > r - l + 1) {20                     len = r - l + 1;21                     idx = l;22                 }23                 times[s[l]]++;24                 if (exist[s[l]] && times[s[l]] > 0) n++;25                 l++;26             }27         }28         return len == INT_MAX ? "" : s.substr(idx, len);29     }30 };