hdu 1162 Eddy's picture

#include<iostream>
#include<cmath>
#define N 999999
double map[101][101];
int visited[101];
double mark[101];
int n;
using namespace std;
double dit (double x1,double y1,double x2, double y2)
{
	return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}
double prim()
{
	int i,j,k;
	double sum=0,min;
	memset(mark,0,sizeof(mark));
	memset(visited,0,sizeof(visited));
	k=1;
	visited[k]=1;
	for(i=2;i<=n;i++)
	{
		mark[i]=map[k][i];               //计算k到各顶点的距离
	}
	min=N;

	for(i=1;i<=n-1;i++)                  
	{
		for(j=1;j<=n;j++)
			if(mark[j]<min&&!visited[j])
			{
				min=mark[j];
				k=j;
			}

		visited[k]=1;

		for(j=1;j<=n;j++)
		{
			if(mark[j]>map[k][j]&&!visited[j])
				mark[j]=map[k][j];
		}
	
		sum+=min;
		min=N;
	}

	return sum;

}

int main()
{
	int i,j;
	double x[101],y[101];
	while(cin>>n)
	{
		for(i=1;i<=n;i++)
			cin>>x[i]>>y[i];

		memset(map,0,sizeof(map));

		for(i=1;i<=n-1;i++)
		{
			for(j=i+1;j<=n;j++)
			{
				map[i][j]=map[j][i]=dit(x[i],y[i],x[j],y[j]);
			}

		}
		printf("%.2lf\n",prim());

	}
	return 0;
}