poj 2031 Building a Space Station

简单最小生成树 注意建图

#include <iostream>#include <cstring>#include <cmath>#define inf 100000000#define eps 1e-8using namespace std;int n;double map[150][150],lowc[150];bool vis[150];struct node{double x,y,z,r;}cell[150];double dis(node a,node b){return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z));}double prim(){int i,j,p;double minc,res=0;memset(vis,0,sizeof(vis));vis[0]=1;for(i=1;i<n;i++)lowc[i]=map[0][i];for(i=1;i<n;i++){minc=inf;p=-1;for(j=0;j<n;j++)if(vis[j]==0 && minc>lowc[j]){minc=lowc[j];p=j;}if(inf==minc)return -1;res+=minc;vis[p]=1;for(j=0;j<n;j++)if(vis[j]==0 && lowc[j]>map[p][j])lowc[j]=map[p][j];}return res;}int main(){int i,j;double d;while(scanf("%d",&n)!=EOF && n){for(i=0;i<n;i++)scanf("%lf%lf%lf%lf",&cell[i].x,&cell[i].y,&cell[i].z,&cell[i].r);for(i=0;i<n;i++)for(j=0;j<n;j++){d=dis(cell[i],cell[j]);if(d-cell[i].r-cell[j].r>eps)map[i][j]=d-cell[i].r-cell[j].r;elsemap[i][j]=0;}printf("%.3lf/n",prim());}return 0;}