hdu 1162 Eddy's picture

http://acm.hdu.edu.cn/showproblem.php?pid=1162

#include <cstdio>
#include <cstring>
#include <iostream>
#include <cmath>
#include <algorithm>
#define maxn 200
using namespace std;
const int inf=1<<30;

double g[maxn][maxn];
int n;
bool vis[maxn];
double dist[maxn];
double sum;
struct node
{
    double x,y;
}p[maxn];

double sqr(double x)
{
    return x*x;
}

double dis(int x1,int y1,int x2,int y2)
{
    return sqrt(sqr(x1-x2)+sqr(y1-y2));
}

void prim()
{
    memset(vis,false,sizeof(vis));
    for(int i=1; i<=n; i++) dist[i]=g[1][i];
    dist[1]=0;
    vis[1]=true;
    for(int i=1; i<n; i++)
    {
        double m=(double)inf;
        int x;
        for(int j=1; j<=n; j++) if(!vis[j]&&dist[j]<m) m=dist[x=j];
        sum+=m;
        vis[x]=true;
        for(int j=1; j<=n; j++) if(!vis[j]) dist[j]=min(dist[j],g[x][j]);
    }
}


int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1; i<=n; i++)
        {
            cin>>p[i].x>>p[i].y;
        }
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=n; j++)
            {
                double d=dis(p[i].x,p[i].y,p[j].x,p[j].y);
                g[i][j]=g[j][i]=d;
            }
        }
        sum=0;
        prim();
        printf("%.2lf
",sum);
    }
    return 0;
}