/**
knakul853
**/

class Solution {
public:
    string minWindow(string s, string t) {

        int n = (int)s.size();
        int rem = (int)t.size();
        vector<int>dict(256,0);

        for(char c:t)dict[c]++; // mark the all pattern in dictionary

        int ans = INT_MAX;
        int start = INT_MAX;
        int l=0;
        int i=0;
        while( i < n )
        {
            dict[s[i]]--; // counter the presence of the current character.

            if(dict[s[i++]]>=0) rem--; // if current character mached dec..it's frequencies


            while(rem == 0) // we got the match exctract it's length.
            {
                if( ans > i-l)
                {
                    ans = i-l;
                    start = l;
                }

                dict[s[l]]++;
                if(dict[s[l++]] > 0) rem++;  // try to decrease it's lenth as much as possible.
            }
        }


        return ans==INT_MAX ? "":s.substr(start, ans);

    }
};