HDU 3371(城市联通 最小生成树-Kruskal)

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <algorithm> /*rank 是algorithm里的*/
 4 using namespace std;
 5 int father[100005],r[100005];
 6 int n,m,k,ans;
 7 struct edg
 8 {
 9     int from,to,money;
10 }e[100005];
11 int fd(int x)
12 {
13     if(x==father[x])   return x;
14     return fd(father[x]);
15 }
16 void makeset(int x)
17 {
18     for(int i = 1; i <= x;i++)
19     {
20         father[i] = i;
21         r[i] = 1;
22     }
23 }
24 void uon(int x,int y)
25 {
26     x = fd(x);
27     y = fd(y);
28     if(x!=y)
29     {
30         if(r[x] >= r[y])
31         {
32             father[y] = x;
33             r[x] += r[y];
34             r[y] = 0;
35         }
36         else
37         {
38             father[x] = y;
39             r[y] += r[x];
40             r[x] = 0;
41         }
42     }
43 }
44 bool cmp(edg x,edg y)
45 {
46     return x.money < y.money;
47 }
48 int main()
49 {
50     int t,p,len;
51     scanf("%d",&t);
52     while(t--)
53     {
54         scanf("%d%d%d",&n,&m,&k);
55         makeset(n);
56         ans = 0;
57         len = 0;
58         for(int i = 1; i <= m; i++)
59             scanf("%d%d%d",&e[i].from,&e[i].to,&e[i].money);
60         for(int i = 1; i <= k; i++)
61         {
62             scanf("%d",&p);
63             int a,b(0);
64             for(int u = 0; u < p ;u++)
65             {
66                 scanf("%d",&a);
67                 if(u&&b)    uon(a,b);
68                 b = a;
69             }
70         }
71         sort(e+1,e+1+m,cmp);
72         for(int i = 0; i < m; i++)
73             if(fd(e[i].from)!=fd(e[i].to))
74             {
75                 uon(e[i].from,e[i].to);
76                 ans += e[i].money;
77             }
78         for(int i = 1; i <= n; i++)
79             if(r[i] > 0)    len++;  //检查所有点是否只有一个根，即是否存在未连在树上的点
80         if(len == 1)    printf("%d\n",ans);
81         else    printf("-1\n");
82     }
83     return 0;
84 }