题目：

题解：

void swap(char* a, char* b) {char tmp = *a;*a = *b, *b = tmp;
}void reverse(char* l, char* r) {while (l < r) {swap(l++, --r);}
}int min(int a, int b) {return a < b ? a : b;
}char* reverseStr(char* s, int k) {int n = strlen(s);for (int i = 0; i < n; i += 2 * k) {reverse(&s[i], &s[min(i + k, n)]);}return s;
}