{

string res = "";

int minWinSize = INT_MAX;

int lengthT = t.size(); //the length of string t

unordered_map<char, int> mapT, mapTemp; //strT is a map of string t; strTtemp is a map of substr

for (auto ch : t)

{

++mapT[ch];

//strTtemp[ch]=0;

}

queue<int> qS;

int lengthTemp = 0;

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

{

if (mapT.find(s[i]) != mapT.end())

{

qS.push(i);

++mapTemp[s[i]];

if (mapTemp[s[i]] <= mapT[s[i]]) ++lengthTemp; //if substr doesn't have enough same characters, ++lengthTemp

//ready to pop from qS

while (lengthTemp == lengthT)

{

int popIndex = qS.front();

char popChar = s[popIndex];

qS.pop();

if (minWinSize > i - popIndex + 1)

{

minWinSize = i - popIndex + 1;

res = s.substr(popIndex, minWinSize);

}

--mapTemp[popChar];

if (mapTemp[popChar] < mapT[popChar])

--lengthTemp;

}

}

}

return res;

{

string s = "ADOBECODEBANC";

string t = "ABC";

string res = minWindow(s, t);

std::cout << "Hello World!\n";