poj 2031 Building a Space Station(最小生成树)

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#include<cstdio>#include<cstring>#include<cmath>#include<algorithm>using namespace std;struct d{    int u,v;    double w;} e[10000+5];bool cmp(d a,d b){    return a.w<b.w;}int bin[100+5];double x[100+5],y[100+5],z[100+5],r[100+5];int Find(int x){    int s;    for(s=x; bin[s]>=0; s=bin[s]);    while(s!=x)    {        int t=bin[x];        bin[x]=s;        x=t;    }    return s;}void Union(int x1,int x2){    int f1=Find(x1),f2=Find(x2);    int t=bin[f1]+bin[f2];    if(bin[f1]>bin[f2])    {        bin[f1]=f2;        bin[f2]=t;    }    else    {        bin[f2]=f1;        bin[f1]=t;    }}int main(){    int n,m,i,j,u,v;    double ans;    while(~scanf("%d",&n)&&n)    {        for(i=0; i<n; i++)            bin[i]=-1;        for(i=0; i<n; i++)            scanf("%lf%lf%lf%lf",&x[i],&y[i],&z[i],&r[i]);        for(i=0,m=0; i<n; i++)            for(j=i+1; j<n; j++)            {                double t=(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j])+(z[i]-z[j])*(z[i]-z[j]);                t=sqrt(t);                if(t<=r[i]+r[j])                {                    if(Find(i)!=Find(j)) Union(i,j);                }                else                {                    e[m].u=i;                    e[m].v=j;                    e[m].w=t-r[i]-r[j];                    m++;                }            }            sort(e,e+m,cmp);        for(ans=0,i=0; i<m; i++)        {            u=e[i].u;            v=e[i].v;            if(Find(u)!=Find(v))            {                ans+=e[i].w;                Union(u,v);            }        }        printf("%.3f\n",ans);    }    return 0;}
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