杭电1217--Arbitrage(Spfa)

 1 #include <map>
 2 #include <queue>
 3 #include <cmath>
 4 #include <cstdio>
 5 #include <cstring>
 6 #include <iostream>
 7 using namespace std;
 8 const int INF = 0x3f3f3f3f;
 9 double ap[33][33], dis[33]; int vis[33];
10 map<string, int> mmap;
11 int n;
12 bool Spfa(int src)
13 {
14     memset(vis, 0, sizeof(vis));
15     for(int i = 1; i <= n; i++)
16         dis[i] = 0.0;
17     dis[src] = 1.0; vis[src] = 1;  //****************//
18     queue<int> q;
19     q.push(src);
20     while(!q.empty())
21     {
22         int temp = q.front();
23         q.pop();
24         vis[temp] = 0;
25         for(int j = 1; j <= n; j++)
26         {
27             if(dis[j] < dis[temp] * ap[temp][j])
28             {
29                 dis[j] = dis[temp] * ap[temp][j];
30                 if(!vis[j])
31                     q.push(j);
32                 vis[j] = 1;
33                 if(dis[src] > 1.0)
34                     return true;
35             }
36         }
37     }
38     return false; 
39 }
40 int main()
41 {
42     int Q = 1;
43     while(~scanf("%d", &n), n)
44     {
45         memset(ap, 0, sizeof(ap)); 
46         mmap.clear(); string mon;
47         for(int i = 1; i <= n; i++)   //无向图边权关系存储， 按照有向图来存也可。 
48         {
49             cin >> mon;
50             mmap[mon] = i;
51         }
52         int m;
53         scanf("%d", &m);
54         string a, b; double oo;
55         for(int i = 1; i <= m; i++)
56         {
57             cin >> a >> oo >>b;
58             ap[mmap[a]][mmap[b]]=oo;
59         } 
60         if(Spfa(1))        
61             printf("Case %d: Yes\n", Q++);        
62         else         
63             printf("Case %d: No\n", Q++);
64     }
65     return 0;
66 }

 1 #include <map>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 using namespace std;
 6 const int INF = 0x3f3f3f3f;
 7 map<string, int> mmap;
 8 double ap[33][33];
 9 int n;
10 bool Floyd()
11 {
12     for(int k = 1; k <= n; k++)
13         for(int i = 1; i <= n; i++)
14             for(int j = 1; j <= n; j++)
15                 if(ap[i][j] < ap[i][k] * ap[k][j]){
16                     ap[i][j] = ap[i][k] * ap[k][j];
17             //        printf("%.4lf\n", ap[i][j]);
18                 }
19     for(int i = 1; i <= n; i++)  //*******************// 
20         if(ap[i][i] > 1)
21             return true;
22     return false;
23 }
24 int main()
25 {
26     int Q = 1;  
27     while(~scanf("%d", &n), n)
28     {
29         mmap.clear();
30         for(int i = 1; i <= n; i++)
31             for(int j = 1; j <= n; j++)
32                 ap[i][j]=(i==j?0:INF); 
33         memset(ap, 0, sizeof(ap));
34         string mon; int k = 1;
35         for(int i = 0; i < n; i++){
36             cin >> mon;
37             mmap[mon] = k++;
38         }
39         int m;
40         scanf("%d", &m);
41         for(int i = 0; i < m; i++){
42             string a, b; double oo;
43             cin >>a >> oo >> b;
44             ap[mmap[a]][mmap[b]]=oo;
45             if(ap[mmap[a]][mmap[b]] > oo)
46                 ap[mmap[a]][mmap[b]]=ap[mmap[b]][mmap[a]]=oo;
47         }
48         if(Floyd())
49             printf("Case %d: Yes\n", Q++);
50         else
51             printf("Case %d: No\n", Q++); 
52     } 
53     return 0;
54 }