text: class Solution {
  public:
      string minWindow(string s, string t) {
          unordered_map<char, int>m;
          int i = 0, j = 0, count = 0, minLen = INT_MAX;
          string res = "";
          for(auto x: t) m[x]++, count++;
          while(j < s.size()){
              if(m[s[j++]]-- > 0) count--;
              if(count == 0){
                  while(m[s[i]] < 0) m[s[i++]]++;
                  int len = j - i;
                  if(len < minLen){
                      minLen = len;
                      res = s.substr(i, len);
                  }
                  m[s[i++]]++;
                  count++;
              }
          }
          return res;
      }
  };
  