题目：

题解：

class Solution {
public:unordered_map <char, int> ori, cnt;bool check() {for (const auto &p: ori) {if (cnt[p.first] < p.second) {return false;}}return true;}string minWindow(string s, string t) {for (const auto &c: t) {++ori[c];}int l = 0, r = -1;int len = INT_MAX, ansL = -1, ansR = -1;while (r < int(s.size())) {if (ori.find(s[++r]) != ori.end()) {++cnt[s[r]];}while (check() && l <= r) {if (r - l + 1 < len) {len = r - l + 1;ansL = l;}if (ori.find(s[l]) != ori.end()) {--cnt[s[l]];}++l;}}return ansL == -1 ? string() : s.substr(ansL, len);}
};