HDU 3371 Connect the Cities

题解：最小生成树

#include <cstdio>

#include <algorithm>

using namespace std;

struct node{int a,b,l;}seg[25005];

int T,z,x,t,f[505],m,n,k; char c;

int sf(int x){return f[x]==x?x:f[x]=sf(f[x]);}

bool cmp(node a,node b){return a.l<b.l;}

void scan(int &x){

    while(c=getchar(),c<'0'||c>'9');x=c-'0';

    while(c=getchar(),c>='0'&&c<='9')x=x*10+c-'0';

}

int main(){

    scan(T);

    while(T--){

        scan(n),scan(m),scan(k);

        int ans=0;

        for(int i=1;i<=n;i++)f[i]=i;

        int cnt=n-1;

        for(int i=0;i<m;i++)scan(seg[i].a),scan(seg[i].b),scan(seg[i].l);

        while(k--){

            scan(t);scan(x);

            int q=sf(x);

            for(int i=1;i<t;i++){

                scan(z);

                int w=sf(z);

                if(q!=w)f[w]=q,cnt--;

            }

        }sort(seg,seg+m,cmp);

        for(int i=0;i<m&&cnt;i++){

            int q=sf(seg[i].a),w=sf(seg[i].b);

            if(q!=w)cnt--,f[q]=w,ans+=seg[i].l;

        }

        if(cnt)puts("-1");else printf("%d\n",ans);

    }

    return 0;

}