题目：

题解：

char* minWindow(char* s, char* t) {int tLen = strlen(t);int hash[256] = { 0 };for (int i = 0; i < tLen; ++i)++hash[t[i]];for (int i = 0; i < 256; ++i) {if (0 == hash[i])hash[i] = INT_MIN;}int left, right, count, start, minLen, sLen;left = right = count = 0;start = -1;minLen = INT_MAX;sLen = strlen(s);for (right; right < sLen; ++right) {if (hash[s[right]] > INT_MIN) {if (hash[s[right]] > 0)++count;--hash[s[right]];}if (count == tLen) {while (hash[s[left]] < 0) {if (hash[s[left]] > INT_MIN)++hash[s[left]];++left;}if (right - left + 1 < minLen) {minLen = right - left + 1;start = left;}++hash[s[left]];++left;--count; //注意只丢弃第一个字符}}if (start == -1) {char* ans = (char*)malloc(sizeof(char));if (ans) {*ans = '\0';return ans;}}else {char* ans = (char*)malloc(sizeof(char) * minLen + 1);if (ans) {int i = 0, j = start;for (i; i < minLen; ++i) {ans[i] = s[j];++j;}ans[minLen] = '\0';return ans;}}return NULL;
}