标签：hdu4463   outlets   次小生成树   prim   

Outlets

4
2 3
0 0
1 0
0 -1 
1 -1
0

3.41

数据范围小。水的不能再水，没什么可说的，就是次小生成树

#include <stdio.h>
#include <string.h>
#include <cmath>
#define MAX 60

const double INF = 1000000000.0 ;

struct Point{
	int x,y;
}p[MAX];

double graph[MAX][MAX] ,max[MAX][MAX] ;
bool used[MAX][MAX] , visited[MAX];

double prim(int n)
{
	int closest[MAX];
	double lowCost[MAX] , sum = 0.0;
	memset(visited,false,sizeof(visited)) ;
	memset(max,0,sizeof(max)) ;
	memset(used,false,sizeof(used)) ;
	for(int i = 1 ; i <= n ; ++i)
	{
		lowCost[i] = graph[1][i] ;
		closest[i] = 1 ;
	}
	visited[1] = true ;
	for(int i = 0 ; i < n-1 ; ++i)
	{
		double min = INF ;
		int index = -1 ;
		for(int j = 1 ; j <= n ; ++j)
		{
			if(!visited[j] && lowCost[j]<min)
			{
				min = lowCost[j];
				index = j ;
			}
		}
		if(index == -1)
		{
			break ;
		}
		sum += lowCost[index] ;
		visited[index] = true ;
		used[index][closest[index]] = used[closest[index]][index] = true ;
		for(int j = 1 ; j <= n ; ++j)
		{
			if(visited[j] && j != index)
			{
				max[j][index] = max[index][j] = lowCost[index]>max[j][closest[index]]?lowCost[index]:max[j][closest[index]] ;
			}
			if(!visited[j] && lowCost[j]>graph[index][j])
			{
				lowCost[j] = graph[index][j] ;
				closest[j] = index ; 
			}
		}
	}
	return sum ;
}

double dis(const Point &p1 , const Point &p2)
{
	int x = p1.x-p2.x , y = p1.y-p2.y ;
	return sqrt((x*x+y*y)*1.0) ;
}

int main()
{
	int n ;
	while(~scanf("%d",&n) && n)
	{
		Point p[MAX] ;
		int pt,qt;
		scanf("%d%d",&pt,&qt);
		for(int i = 1 ; i <= n ; ++i)
		{
			scanf("%d%d",&p[i].x,&p[i].y) ;
		}
		for(int i = 1 ; i <= n ; ++i)
		{
			graph[i][i] = 0 ;
			for(int j = 1 ; j < i ; ++j)
			{
				graph[i][j] = graph[j][i] = dis(p[i],p[j]) ;
			}
		}
		double sum = prim(n) ;
		if(used[pt][qt])
		{
			printf("%.2lf\n",sum) ;
		}
		else
		{
			printf("%.2lf\n",sum+graph[pt][qt]-max[pt][qt]) ;
		}
	}
	return 0 ;
}

hdu 4463 Outlets Prim 次小生成树 简单题

标签：hdu4463   outlets   次小生成树   prim   

原文地址：http://blog.csdn.net/lionel_d/article/details/43915839