杭電8-Ink on paper

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思路：

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
#include<map>
#include<queue>
#include<math.h>
#include<vector>
using namespace std;
#define ll long long
struct node{
    ll x,y;
}e[5010];
ll dis[5010];
int vis[5010];
int n;

ll prim()
{
    memset(dis,0,sizeof(dis));
    memset(vis,0,sizeof(vis));
    ll ans = 0;
    vis[1] = 1;
    for(int i = 1; i <= n; i++)
    if(!vis[i])
    dis[i] = pow(abs(e[1].x-e[i].x),2)+pow(abs(e[1].y-e[i].y), 2);
    
    for(int i = 1; i <= n; i++)
    {
        int flag = 0;
        ll minn = 1e18+1;
        for(int j = 1; j <= n; j++)
        {
            if(!vis[j] && dis[j] < minn)
            {
                flag = j,minn = dis[j];
            }
        }
        ans = max(ans, dis[flag]);
        vis[flag] = 1;
        for(int j = 1; j <= n; j++)
        {
            if(!vis[j])
            dis[j] = min(dis[j], (ll)pow(abs(e[flag].x-e[j].x),2) + (ll)pow(abs(e[flag].y-e[j].y),2));
        }
    }
    return ans;
}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        scanf("%d",&n);
        for(int i = 1; i <= n; i++)
        {
            ll op1,op2;
            scanf("%lld%lld",&op1,&op2);
            e[i].x = op1,e[i].y = op2;
        }
        printf("%lld\n",prim());
    }
}