Connect the Cities(MST prim)

 1 #include<stdio.h>
 2 #include<string.h>
 3 using namespace std;
 4 #define N 505
 5 #define INF 0x7fffffff
 6 int n , m , k ;
 7 int g[N][N] , vis[N] , low[N] ;
 8 
 9 void prim ()
10 {
11     int pos = 1 , res = 0 ;
12     memset (vis , 0 , sizeof(vis)) ;
13     vis[pos] = 1 ;
14     for (int i = 1 ; i <= n ; i++)
15         if ( !vis[i] )
16             low[i] = g[pos][i] ;
17     for (int i = 1 ; i < n ; i++) {
18         int minn = INF ;
19         pos = -1 ;
20         for (int j = 1 ; j <= n ; j++)
21             if ( !vis[j] && low[j] < minn) {
22                 minn = low[j] ;
23                 pos = j ;
24         }
25         if (pos == -1) {
26             puts ("-1") ;
27             return ;
28         }
29         res += minn ;
30         vis[pos] = 1 ;
31         for (int j = 1 ; j <= n ; j++)
32             if (!vis[j] && low[j] > g[pos][j])
33                 low[j] = g[pos][j] ;
34     }
35     printf ("%d\n" , res) ;
36 }
37 int main()
38 {
39    // freopen ("a.txt" , "r" , stdin);
40     int u , v , w ;
41     int T , t;
42     scanf ("%d" , &T) ;
43     while (T--) {
44         scanf ("%d%d%d" , &n , &m , &k) ;
45         for (int i = 0 ; i <= n ; i++)
46             for (int j = 0 ; j <= n ; j++)
47                 g[i][j] = INF ;
48         for (int i = 0 ; i < m ; i++) {
49             scanf ("%d%d%d" , &u , &v , &w) ;
50             if (g[u][v] > w)//notice
51                 g[u][v] = g[v][u] = w ;
52         }
53         for (int i = 0 ; i < k ; i++) {
54             scanf ("%d%d" , &t , &u) ;
55             for (int j =1 ; j <= t - 1 ; j++) {
56                 scanf ("%d" , &v) ;
57                 g[u][v] = g[v][u] = 0 ;
58             }
59         }
60         prim () ;
61     }
62 }