POJ3771+Prim

来源：互联网发布：嘉兴学院网络教育编辑：程序博客网时间：2024/06/14 04:36
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;elsemat[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;}