zoj1718 Building a Space Station poj2031

#include <iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#define MAXN 101
#define MAXM 10000
using namespace std;
struct edge
{
    int u,v;
    double w;
}edges[MAXM];
int parent[MAXN];
int N,M;
double X[MAXN],Y[MAXN],Z[MAXN],R[MAXN];
int i,j;
double sumweight;
void UFset()
{
    for(i=0; i<N; i++)
    {
        parent[i]=-1;
    }
}
int Find(int x)
{
    int s;
    for(s=x; parent[s]>0;s=parent[s]);
    while(s!=x)
    {
        int tmp=parent[x];
        parent[x]=s;
        x=tmp;
    }
    return s;
}
void Union(int R1,int R2)
{
    int r1=Find(R1);
    int r2=Find(R2);
    int tmp=parent[r1]+parent[r2];
    if(parent[r1]<parent[r2])
    {
        parent[r2]=r1;
        parent[r1]=tmp;
    }
    else
    {
        parent[r1]=r2;
        parent[r2]=tmp;
    }
}
int cmp(const void *a,const void *b)
{
    edge aa=*(const edge *)a;
    edge bb=*(const edge *)b;
    if(aa.w>bb.w)
    return 1;
    else return -1;
}
void Kruskal()
{
    int num=0;
    int u,v;
    UFset();

    for(i=0;i<M;i++)
    {
         u=edges[i].u;
         v=edges[i].v;
         if(Find(u)!= Find(v))
         {
             sumweight+=edges[i].w;
             num++;

             Union(u,v);

         }
         if(num==N-1)break;

    }
}
int main()
{
    double d;
    while(scanf("%d",&N)!=EOF&&N!=0)
    {
        for(i=0; i<N; i++)
        {
            scanf("%lf%lf%lf%lf",&X[i],&Y[i],&Z[i],&R[i]);
        }

        int mi=0;
        for(i=0; i<N; i++)
        {
            for(j=i+1; j<N; j++)
            {
                d=sqrt((X[i]-X[j])*(X[i]-X[j])+(Y[i]-Y[j])*(Y[i]-Y[j])+(Z[i]-Z[j])*(Z[i]-Z[j]));
                edges[mi].u=i;
                edges[mi].v=j;
                if(d-R[i]-R[j]>0)
                {
                    edges[mi].w=d-R[i]-R[j];
                }
                else {edges[mi].w=0;}
                mi++;
            }
        }

        M=mi;
        qsort(edges,M,sizeof(edges[0]),cmp);
        sumweight=0.0;
        Kruskal();
        printf("%.3lf
",sumweight);
    }
    return 0;
}