class Solution {

public:

string minWindow(string s, string t) {

unordered_map<char, int> mpSrc;

unordered_map<char, int> mpCur;

int nFindLen = 0;

queue<int> qIndex;

for (auto ch : t)

{

mpSrc[ch]++;

}

int nWinLeft = -1;

int nWinRight = s.size();

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

{

if (mpSrc.count(s[i]) == 0)

continue;

mpCur[s[i]]++;

qIndex.push(i);

if (mpCur[s[i]] <= mpSrc[s[i]]) nFindLen++;

if (nFindLen == t.size())

{

int k = 0;

do

{

k = qIndex.front();

qIndex.pop();

mpCur[s[k]]--;

} while (mpCur[s[k]] >= mpSrc[s[k]]);

if (i - k < nWinRight - nWinLeft)

{

nWinRight = i;

nWinLeft = k;

}

nFindLen--;

}

}

return nWinLeft == -1 ? "" : s.substr(nWinLeft, nWinRight - nWinLeft + 1);

}

};