UVa:10397 Connect the Campus（最小生成树）

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include <cmath>
#define MAXN 755
using namespace std;
struct Edge
{
    int a,b;
    double weight;
};
bool vis[1005][1005];
Edge p[MAXN*MAXN];
int father[MAXN];
bool cmp(Edge x,Edge y)
{
    return x.weight<y.weight;
}
int find(int p)
{
    return p==father[p]?p:(father[p]=find(father[p]));
}
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        int x[MAXN],y[MAXN];
        memset(vis,0,sizeof(vis));
        for(int i=1; i<=n; ++i)
            scanf("%d%d",&x[i],&y[i]);
        int m;
        scanf("%d",&m);
        for(int i=0; i<m; ++i)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            vis[u][v]=true;
        }
        int N=0;
        for(int i=1; i<n; ++i)
            for(int j=i+1; j<=n; ++j)
            {
                p
.a=i;
                p
.b=j;
                p[N++].weight=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
            }
        sort(p,p+N,cmp);
        for(int i=0; i<=n; ++i)
            father[i]=i;
        double ans=0;
        for(int i=0; i<N; ++i)
        {
            int  ta=p[i].a,tb=p[i].b;
            if(vis[ta][tb]||vis[tb][ta])
                father[find(ta)]=find(father[tb]);
        }
        for(int i=0; i<N; ++i)
        {
            int  ta=p[i].a,tb=p[i].b;
            if(find(ta)!=find(tb))
            {
                ans+=p[i].weight;
                father[find(ta)]=find(father[tb]);
            }
        }
        printf("%.2lf\n",ans);
    }
    return 0;
}