POJ3771+Prim

最小生成树的应用

数据量小。

/*

Prim

*/

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

#include<algorithm>

#include<iostream>

#include<queue>

#include<map>

#include<stack>

#include<set>

#include<math.h>

using namespace std;

typedef long long int64;

//typedef __int64 int64;

typedef pair<int64,int64> PII;

#define MP(a,b) make_pair((a),(b)) 

const int maxn = 55;

const double inf = 99999999;

const double pi=acos(-1.0);

const double eps = 1e-8;



struct Node{

	double x,y;

}pnt[ maxn ];

double dis[ maxn ];

bool vis[ maxn ];

double mat[ maxn ][ maxn ];

double dist( int a,int b ){

	return sqrt( (pnt[a].x-pnt[b].x)*(pnt[a].x-pnt[b].x)+(pnt[a].y-pnt[b].y)*(pnt[a].y-pnt[b].y) );

}



double Prim( int start,int aim,int n ){

	double ans = 0;

	memset( vis,false,sizeof( vis ) );

	vis[ start ] = true;

	vis[ aim ] = true;

	for( int i=0;i<n;i++ ){

		dis[ i ] = mat[ start ][ i ];

	}

	for( int i=0;i<n;i++ ){

		int id = -1;

		double M = inf;

		for( int j=0;j<n;j++ ){

			if( vis[ j ]==false&&M>dis[ j ] ){

				M = dis[ j ];

				id = j;

			}

		}

		if( id==-1 ) break;

		vis[ id ] = true;

		ans += M;

		for( int j=0;j<n;j++ ){

			if( vis[ j ]==false&&dis[ j ]>mat[ id ][ j ] ){

				dis[ j ] = mat[ id ][ j ];

			}

		}

	}

	return ans ;

}	



int main(){

	int T;

	scanf("%d",&T);

	while( T-- ){

		int n;

		scanf("%d",&n);

		for( int i=0;i<n;i++ ){

			scanf("%lf%lf",&pnt[i].x,&pnt[i].y);

		}

		if( n==1 ){

			puts("0");

			continue;

		}

		for( int i=0;i<n;i++ ){

			for( int j=0;j<n;j++ ){

				if( i==j )

					mat[i][j] = 0.0;

				else

					mat[i][j] = dist( i,j );

			}

		}

		double res = inf; 

		for( int i=0;i<n;i++ ){

			res = min( res,Prim( (i+1)%n,i,n ) );

		}

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

	}

	return 0;

}