Poj1751--Highways(Prim)

 1 #include <cmath>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 using namespace std;
 6 const int INF = 0x3f3f3f3f;
 7 double a[800], b[800], map[800][800], dis[800]; int vis[800];
 8 int n;
 9 void Prim()
10 {
11     for(int i = 1; i <= n; i++){
12         dis[i] = map[1][i];
13         vis[i] = 1;
14     }
15     dis[1] = 0; vis[1] = -1;
16     for(int i = 0; i< n-1; i++)
17     {
18         int temp = -1; double min = INF;
19         for(int j = 1; j <= n; j++)
20         {
21             if(vis[j] != -1 && min > dis[j])
22             {
23                 temp = j;
24                 min = dis[j];
25             }
26         }
27         
28         if(temp != -1 && dis[temp] != 0)
29             printf("%d %d\n", temp, vis[temp]);
30             vis[temp] = -1;
31         for(int j = 1; j <= n; j++)
32         {
33             if(vis[j] != -1 && dis[j] > map[temp][j]){
34                 dis[j] = map[temp][j]; vis[j] = temp;
35             }    
36         }    
37     }
38     //printf("-1\n");
39 }
40 
41 int main()
42 {
43     scanf("%d", &n);
44     for(int i = 1; i <= n; i++)
45         scanf("%lf %lf", &a[i], &b[i]);
46     for(int i = 1; i <= n; i++)
47         for(int j = 1; j <= n; j++){
48             double temp = sqrt((a[i]-a[j])*(a[i]-a[j])+(b[i]-b[j])*(b[i]-b[j]));
49                 map[i][j] = map[j][i] = temp;
50         }    
51     int m;
52     scanf("%d", &m);
53     for(int i = 1; i <= m; i++){
54         int a, b;
55         scanf("%d %d", &a, &b);
56         map[a][b]=map[b][a]=0;
57             
58     }
59     Prim();
60     return 0;
61 }