uva442Matrix Chain Multiplication（栈）

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<string>
 5 #include<stack>
 6 #include<cctype>
 7 using namespace std;
 8 
 9 struct matrix
10 {
11     int a,b;
12     matrix (int x=0,int y=0):a(x),b(y) {}
13 }m[26];
14 int main()
15 {
16     int n;
17     char ch;
18     string ss;
19     while(scanf("%d",&n)!=EOF&&n)
20     {
21         for(int i=0;i<n;i++)
22         {
23             cin>>ch;
24             scanf("%d%d",&m[ch-'A'].a,&m[ch-'A'].b);
25         }
26        while( cin>>ss )
27         {
28             int ans=0;
29             int ok=0;
30             stack<matrix> s;
31             while(!s.empty()) s.pop();
32             int len=ss.length();
33             for(int i=0;i<len;i++)
34             {
35             if(isalpha(ss[i])) s.push(m[ss[i]-'A']);
36             else if(ss[i]==')')
37             {
38                 matrix m2=s.top();
39                 s.pop();
40                 matrix m1=s.top();
41                 s.pop();
42                 if(m1.b!=m2.a) {ok=1;break;}
43                 ans+=m1.a*m1.b*m2.b;
44                 s.push(matrix(m1.a,m2.b));
45             }
46 
47         }
48         if(!ok) printf("%d
",ans);
49         else puts("error");
50     }
51     }
52 }