hdu1162-Eddy's picture

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

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>

using namespace std;

#define MAX 5050
int fa[ MAX ] ;
struct node
{
int x , y ;
double value ;
bool operator < (const node &T) const
{
return value < T.value;
}
}edge[ MAX ];

struct point
{
double x , y ;
}point[ MAX ];

int Union( int n )
{
for( int i = 0 ; i < n ; ++i )
fa[ i ] = i ;
}
int find( int x )
{
return fa[ x ] = x == fa[ x ] ? x : find( fa[ x ] ) ;
}

int main()
{
int n ;
int i , j ;
while( scanf( "%d" , &n )!= EOF && n )
{
Union( n * n ) ;
for( i = 0 ; i < n ; ++i )
{
scanf( "%lf%lf" , &point[ i ].x , &point[ i ].y ) ;
}
int k = 0 ;
for( i = 0 ; i < n ; ++i )
{
for( j = i + 1 ; j < n ; ++j )
{
edge[ k ].x = i ;
edge[ k ].y = j ;
edge[ k ].value = (double )sqrt( ( point[ i ].x - point[ j ].x ) * ( point[ i ].x - point[ j ].x ) + ( point[ i ].y - point[ j ].y )*(point[ i ].y - point[ j ].y ) );

k++ ;

}
}
sort( edge , edge + k ) ;
double sum = 0.0 ;
for( i = 0 ; i < k ; ++i )
{

int x1 = find( edge[ i ].x ) ;
int x2 = find( edge[ i ].y );
if( x1 != x2 )
{
sum += edge[ i ].value ;
fa[ x1 ] = x2 ;
}
}
printf( "%.2lf\n" , sum ) ;
}
return 0 ;
}