hdu 1217 Arbitrage (spfa算法)

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <map>
 4 #include <queue>
 5 #include <cstring>
 6 using namespace std;
 7 int n,a;
 8 double Map[35][35];
 9 const int INF=9999;
10 map<string,int>V;
11 
12 int spfa()
13 {
14     queue<int>q;
15     double node[35]= {0};
16     int inq[35]= {0};
17     node[1]=1;
18     inq[1]=1;
19     q.push(1);
20     while (!q.empty())
21     {
22         int s=q.front();
23         q.pop();
24         for (int i=1; i<=n; i++)
25         {
26             //cout<<Map[s][i]<<" "<<node[i]<<endl;
27             if (node[i]<Map[s][i]*node[s])
28             {
29                 //cout<<node[i]<<" "<<Map[s][i]<<endl;
30                 node[i]=Map[s][i]*node[s];
31                 if (!inq[i])
32                 {
33                     q.push(i);
34                     inq[i]=1;
35                 }
36                 if (node[1]>1)
37                     return 1;
38             }
39 
40         }
41         inq[s]=0;
42     }
43     return 0;
44 }
45 int main ()
46 {
47     char ch[35];
48     int cmp=1,q;
49     while (scanf("%d",&n),n)
50     {
51         q=0;
52         V.clear();
53         for (int i=1; i<=n; i++)
54             for (int j=1; j<=n; j++)
55                 Map[i][j]=0;
56         //memset(Map,INF,sizeof(Map));
57         for (int i=1; i<=n; i++)
58         {
59             scanf("%s",ch);
60             if (!V[ch])
61                 V[ch]=++q;
62         }
63         scanf("%d",&a);
64         for (int i=1; i<=a; i++)
65         {
66             double money;
67             char ch1[35],ch2[35];
68             scanf("%s%lf%s",ch1,&money,ch2);
69             if (Map[V[ch1]][V[ch2]]<money)
70                 Map[V[ch1]][V[ch2]]=money;
71             //cout<<Map[V[ch1]][V[ch2]]<<endl;
72         }
73         printf ("Case %d: ",cmp++);
74         if (spfa())
75             printf("Yes\n");
76         else
77             printf ("No\n");
78     }
79     return 0;
80 }