class Solution {

public:

string minWindow(string s, string t) {

int l = 0, substr = 0, min_l = 0, min_r = s.size();

map<char, int> cnt;

for(char c : t)

cnt[c]++;

for(int r = 0; r < s.size(); r++) {

if(cnt.find(s[r]) != cnt.end()) {

if(cnt[s[r]] > 0)

substr++;

cnt[s[r]]--;

}

while(substr == t.size()) {

if(r - l < min_r - min_l) {

min_l = l;

min_r = r;

}

if(cnt.find(s[l]) != cnt.end()) {

cnt[s[l]]++;

if(cnt[s[l]] > 0)

substr--;

}

l++;

}

}

string ans = (min_r < s.size() ? s.substr(min_l, min_r - min_l + 1) : "");

return ans;

}

};