P1265 公路修建

洛谷 1265

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
#include<vector>
#define pow1(x) (x)*(x)
using namespace std;
int n;
double zx[5009],zy[5009],dis[5009],ans=0;
bool vis[5009];
int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        double x,y;
        scanf("%lf%lf",&x,&y);
        zx[i]=x,zy[i]=y;
    }
    vis[1]=true;
    for(int i=1;i<=n;i++)
     dis[i]=sqrt(pow1(zx[1]-zx[i])+pow1(zy[1]-zy[i]));

    for(int k=1;k<=n-1;k++)
    {
        int kk;double minn=1e10;
        for(int i=1;i<=n;i++)
        {
            if(!vis[i]&&dis[i]<minn)
            minn=dis[i],kk=i;
        }

        ans+=minn;
        vis[kk]=true;
        for(int i=1;i<=n;i++)
        {
            double len=sqrt(pow1(zx[kk]-zx[i])+pow1(zy[kk]-zy[i]));
            if(!vis[i]&&len<dis[i])
            {
                dis[i]=len;
            }
        }
    }

    printf("%.2lf",ans);
    return 0;
}