hdoj 1596 find the safest rode

 1 #include <stdio.h>
 2 #include <algorithm>
 3 int n, q;
 4 double safe[1010], sa[1010][1010];
 5 int vis[1010];
 6 double max(double x, double y)
 7 {
 8     return x > y ? x : y;
 9 }
10 void dijkstra(int s, int t)
11 {
12     int u, v;
13     for(u = 1; u <= n; u++)
14     {
15         vis[u] = 0;
16         safe[u] = 0.0;
17     }
18     safe[s] = 1.0;
19     while(true)
20     {
21         v= -1;
22         for(u = 1; u <= n; u++)
23             if(!vis[u] && (safe[u]>safe[v] || v==-1))
24                 v = u;
25         if(v == -1)
26             break;
27         vis[v] = 1; 
28         for(u = 1; u <= n; u++)
29         {
30             safe[u] = max(safe[u], safe[v]*sa[v][u]);
31         }
32     }
33     if(safe[t] == 0.0)
34         printf("What a pity!\n");
35     else
36         printf("%.3f\n", safe[t]);
37 }
38 int main()
39 {
40     double s;
41     while(~scanf("%d", &n))
42     {
43         for(int i = 1; i <= n; i++)
44             for(int j = 1; j <= n; j++)
45             {
46                 scanf("%lf", &s);
47                 if(i <= j)
48                     sa[i][j] = sa[j][i] = s;
49             }
50         scanf("%d", &q);
51         while(q--)
52         {
53             int a, b;
54             scanf("%d%d", &a, &b);
55             dijkstra(a, b); 
56         }
57     }    
58     return 0;
59 }