BZOJ 2429 聪明的猴子

kruskal.

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxm 1050
#define maxn 2050
#define maxe 2000050
using namespace std;
long long m,n,w[maxm],x[maxn],y[maxn],tot=0,father[maxn],mx=0;
struct edge
{
    long long u,v,w;
}e[maxe];
bool cmp(edge x,edge y)
{
    return x.w<y.w;
}
void addedge(long long u,long long v)
{
    e[++tot].u=u;
    e[tot].v=v;
    e[tot].w=(x[u]-x[v])*(x[u]-x[v])+(y[u]-y[v])*(y[u]-y[v]);
}
long long getfather(long long x)
{
    if (x!=father[x])
        father[x]=getfather(father[x]);
    return father[x];
}
void kruskal()
{
    sort(e+1,e+tot+1,cmp);
    for (long long i=1;i<=n;i++) father[i]=i;
    for (long long i=1;i<=tot;i++)
    {
        long long f1,f2;
        f1=getfather(e[i].u);f2=getfather(e[i].v);
        if (f1!=f2)
        {
            father[f1]=f2;
            mx=max(mx,e[i].w);
        }
    }
}
int main()
{
    scanf("%lld",&m);
    for (long long i=1;i<=m;i++)
        scanf("%lld",&w[i]);
    scanf("%d",&n);
    for (long long i=1;i<=n;i++)
        scanf("%lld%lld",&x[i],&y[i]);
    for (long long i=1;i<=n;i++)
        for (long long j=i+1;j<=n;j++)
            addedge(i,j);
    kruskal();
    long long ans=0;
    for (long long i=1;i<=m;i++)
    {
        if (w[i]*w[i]>=mx)
            ans++;
    }
    printf("%lld\n",ans);
    return 0;
}