BZOJ 2429: [HAOI2006]聪明的猴子|最小生成树kruskal

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<queue>
#include<vector>
#include<set>
#include<map>
#include<iostream>
#include<algorithm>
#define T 1010
using namespace std;
int sc()
{
	int i=0,f=1; char c=getchar();
	while(c>'9'||c<'0'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9')i=i*10+c-'0',c=getchar();
	return i*f;
}
struct E{int x,y;double d;}e[T*T];
int x[T],y[T],L[T],fa[T],mx;
int m,n,tot=0,sum=0,ans;
bool cmp(E a,E b){return a.d<b.d;}
int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
int main()
{
	m=sc();
	for(int i=1;i<=m;i++)L[i]=sc();
	n=sc();
	for(int i=1;i<=n;i++)
	{
		x[i]=sc(),y[i]=sc();
		for(int j=1;j<i;j++)
		{
			e[++tot].x=j;
			e[tot].y=i;
			e[tot].d=sqrt((double)(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
		}
		fa[i]=i;
	}
	sort(e+1,e+tot+1,cmp);
	for(int i=1;i<=tot;i++)
	{
		int p=find(e[i].x),q=find(e[i].y);
		if(p!=q)
		{
			sum++;
			fa[p]=q;
			if(sum==n-1)mx=e[i].d;
		}
	}
	for(int i=1;i<=m;i++) if((double)L[i]>=mx)ans++;
	cout << ans;
	return 0;
}