题目：biubiu
题意：在字符串中找到最小的覆盖单词的子串，覆盖要求含有单词的全部字符。
通过滑动窗口实现。移动右指针找到符合条件的子串，移动左指针来使最小。

#include<iostream>
#include<string>
#include<vector>
#include<cmath>
#include<map>
#include<unordered_map>
#include<stack>
#include<algorithm>
using namespace std;
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;
		//cout << s.size() << endl;
		while (r <int(s.size())) {  ///size的返回值类型是size_type,
			//cout << "2" << endl;
			if (ori.find(s[++r]) != ori.end()) {
				++cnt[s[r]];
				//cout << s[r] << "**" << cnt[s[r]] << endl;
			}
			//cout << check() << "*#*" << endl;
			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++;
			}

		}
		//cout << "****" << ansL << endl;
		return ansL == -1 ? string() : s.substr(ansL, len);
	}
};
int main() {
	string word1, word2;
	while (cin >> word1 >> word2) {
		Solution s;
		cout << s.minWindow(word1, word2) << endl;
	}
	return 0;
}