[hdu] P7058 Ink on paper 求最小生成树的最大边

题目链接
求最小生成树的最大边。
图是完全图，在稠密图中prim算法更优

#include<bits/stdc++.h>
#define FAST ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
typedef long long ll;
const int maxn = 1e5+5;
const ll INF = 1LL<<60;
using namespace std;

int n,m,tot;
ll dis[5005],mp[5001][5001];
int vis[5005];

struct P
{
    
	ll x,y;
}p[5005];

ll cal(int i, int j){
    
	return (p[i].x-p[j].x)*(p[i].x-p[j].x)+(p[i].y-p[j].y)*(p[i].y-p[j].y);
}

ll prime()
{
    
	int now;
	ll ans;
	
	for (int i=1; i<=n; i++) dis[i]=INF, vis[i]=0;
	dis[1]=0;
	
	tot=0, now=1, ans=-1;
	for (int t=1; t<=n; t++)
	{
    
		ll minn=INF;
		for (int i=1; i<=n; i++){
    
			if (!vis[i] && dis[i]<minn){
    
				minn=dis[i];
				now=i;
			}
		}
		vis[now]=1;
		ans=max(ans,dis[now]);
		
		for (int j=1; j<=n; j++)
			if (!vis[j] && mp[now][j]<dis[j]) dis[j]=mp[now][j]; 
	}
	return ans;
}

void solve()
{
    
	cin>>n;
	
	for (int i=1; i<=n; i++){
    
		for (int j=1; j<=n; j++)
		mp[i][j]=0;
	}
	
	for (int i=1; i<=n; i++)
		cin>>p[i].x>>p[i].y;
		
	for (int i=1; i<=n; i++){
    
		for (int j=i+1; j<=n; j++)
		mp[i][j]=mp[j][i]=cal(i,j);
	}
	
	ll res=prime();
	cout<<res<<endl;
}

int main()
{
    
   	FAST; 
// freopen("1.in","r",stdin);
	int kase;
	cin>>kase;
	while(kase--)
	{
    
		solve();	
	} 
return 0;
}