UVa 673 (括号配对) Parentheses Balance

 1 #include <cstdio>
 2 #include <stack>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 const int maxn = 150;
 7 char s[maxn];
 8 
 9 bool ok(const char& c1, const char& c2)
10 {
11     if(c1 == ‘(‘ && c2 == ‘)‘) return true;
12     if(c1 == ‘[‘ && c2 == ‘]‘) return true;
13     return false;
14 }
15 
16 int main()
17 {
18     //freopen("in.txt", "r", stdin);
19 
20     int n;
21     scanf("%d", &n); getchar();
22     while(n--)
23     {
24         gets(s);
25         stack<char> S;
26         while(!S.empty()) S.pop();
27         int l = strlen(s);
28         if(l % 2 != 0)
29         {
30             puts("No");
31             continue;
32         }
33         bool flag = true;
34         for(int i = 0; i < l; ++i)
35         {
36             if(s[i] == ‘(‘ || s[i] == ‘[‘) S.push(s[i]);
37             else
38             {
39                 if(S.empty()) { flag = false; break; }
40                 else if(ok(S.top(), s[i])) S.pop();
41                 else { flag = false; break; }
42             }
43         }
44         if(!S.empty()) flag = false;
45         printf("%s\n", flag ? "Yes" : "No");
46     }
47 
48     return 0;
49 }