题目链接：hdu_5831_Rikka with Parenthesis II
题意：
给你一些括号的排列，必须交换一次，能不能将全部的括号匹配
题解：
模拟一下括号的匹配就行了，注意要特判只有一对括号是NO，因为必须要交换一次
1 #include <cstdio> 2 #include <cstring> 3 const int N = 1e5 +5; 4 char s[N]; 5 int st[N],top; 6 int main() 7 { 8 int t; 9 scanf("%d", &t); 10 while (t--) 11 { 12 int n; 13 scanf("%d", &n); 14 scanf("%s", s); 15 if (n == 2 && s[0] == '(' && s[1] == ')') {printf("No "); continue;} 16 top = 0; st[0] = -1; 17 for (int i = 0; i < n; i++) 18 { 19 if (s[i] == '(') st[++top] = 0; 20 else if (st[top] == 0) top--; 21 else st[++top] = 1; 22 } 23 if (top == 0) printf("Yes "); 24 else if (top == 2 && st[1] == 1 && st[2] == 0) printf("Yes "); 25 else if (top == 4 && st[1] == 1 && st[2] == 1 && st[3] == 0 && st[4] == 0) printf("Yes "); 26 else printf("No "); 27 } 28 return 0; 29 }