poj-1751 Highways

http://poj.org/problem?id=1751

最小生成树简单应用

#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
#include <math.h>
#include <stack>
#include <queue>

using namespace std;
#define INF 10000000

double map[1110][1110],dis[1110];
int n,m,v[1110],pre[1010],a,b,c,d[1110];

struct node
{
    double x,y;
}p[1010];

double makedis(int i,int j)
{
    return sqrt( 1.0*(p[i].x - p[j].x)*(p[i].x - p[j].x) + 1.0*(p[i].y - p[j].y)*(p[i].y - p[j].y));
}

void prim()
{
	int i, j, k;
	double min, sum = 0;memset(v, 0, sizeof(v));

	for (i = 1; i <= n; i++)
		{
		    dis[i] = map[1][i];
		    pre[i] = 1;
		}

	v[1] = 1;dis[1] = 0;pre[1]= - 1;

	for (i = 2; i <= n; i++)
	{
		k = 1;
		min = INF;
		for (j = 1; j <= n; j++)
			if (!v[j] && min>dis[j])
			{
				k = j;
				min = dis[j];
			}

		sum += min;
		v[k] = 1;
		if (min !=0 )
            cout<<pre[k]<<" "<<k<<endl;

		for (j = 1; j <= n; j++)
			if (!v[j] && dis[j]>map[k][j])
				{
				    dis[j] = map[k][j];
				    pre[j] = k;
				}
	}
}

int main()
{
	scanf("%d",&n);
	{
        for(int i=1;i<=n;i++)
            scanf("%lf%lf",&p[i].x,&p[i].y);

        for(int i=1;i<=n;i++)
            for(int j = 1;j<=n;j++)
        {
            if (i == j)
                map[i][j] = 0;
            else
                map[i][j] = INF;
        }
        for(int i=1;i<=n;i++)
            for(int j = 1;j<=n;j++)
            {
                if (map[i][j] > makedis(i,j))
                {
                    map[i][j] = makedis(i,j);
                    map[j][i] = makedis(i,j);
                }
            }
        scanf("%d",&m);
        while(m--)
        {
            scanf("%d%d",&a,&b);
            map[a][b] = map[b][a] = 0;
        }
        prim();
	}
	return 0;
}