POJ 2031

来源：互联网发布：js可以控制浏览器比例编辑：程序博客网时间：2024/06/11 23:42
#include <iostream>#include <cstdio>#include <algorithm>#include <cstring>#include <cmath>using namespace std;#define esp 10E-9int k,n;int p[105];struct Edge{   int u,v;   double w;}edge[105*105];struct Cor{  double x,y,z,r;}cor[105];bool cmp(Edge a,Edge b){  return a.w<b.w;}int findpa(int x){  return p[x]==x?x:p[x]=findpa(p[x]);}double kruskal(){  for(int i=1;i<=n;i++)  p[i]=i;  double ans=0.0;  int num=0;  sort(edge,edge+k,cmp);  for(int i=0;i<k;i++)  {   int p1=findpa(edge[i].u);   int p2=findpa(edge[i].v);   if(p1!=p2)   {     ans+=edge[i].w;     p[p1]=p2;     num++;   }   if(num==n-1)return ans;  }  return ans;  //很费解，少了这一句之后一直wa。 }int main(){    while(scanf("%d",&n)!=EOF&&n)    {      k = 0;      for(int i = 1; i <= n; i ++)  scanf("%lf%lf%lf%lf",&cor[i].x,&cor[i].y,&cor[i].z,&cor[i].r);  for(int i = 1; i <= n; i ++)  for(int j = i+1; j <=n; j ++)      {        edge[k].u = i;        edge[k].v = j;        edge[k].w = sqrt((cor[i].x-cor[j].x)*(cor[i].x-cor[j].x)+(cor[i].y-cor[j].y)        *(cor[i].y-cor[j].y)+(cor[i].z-cor[j].z)*(cor[i].z-cor[j].z))-cor[i].r-cor[j].r;        if(edge[k].w<=esp)        edge[k].w=0;        k++;      }      double ans=kruskal();      printf("%.3lf\n",ans);    }    return 0;}
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