POJ-2031(最小生成树+kruskal)

Building a Space Station

POJ-2031

注意，这里的输出需要是%f型而不是%lf型的，否则wa.

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
const int maxn=101;
int n;
struct node{
    double x;
    double y;
    double z;
    double r;
};
node cell[maxn];
struct edge{
    int from;
    int to;
    double w;
    bool operator<(const edge& t)const{
        return w<t.w;
    }
};
edge edges[5003];
int set[maxn];
int find(int x){
    return x==set[x]?set[x]:set[x]=find(set[x]);
}
double kruskal(int es){
    double sum=0.000;
    for(int i=0;i<n;i++){
        set[i]=i;
    }
    sort(edges,edges+es);
    for(int i=0;i<es;i++){
        int from=edges[i].from;
        int to=edges[i].to;
        double w=edges[i].w;
        int x=find(from);
        int y=find(to);
        if(x!=y){
            //cout<<from<<" "<<to<<" "<<w<<endl;
            set[x]=y;
            sum+=w;
        }
    }
    return sum;
}
int main(){
    while(cin>>n&&n){
        for(int i=0;i<n;i++){
            scanf("%lf%lf%lf%lf",&cell[i].x,&cell[i].y,&cell[i].z,&cell[i].r);
            // cin>>cell[i].x>>cell[i].y>>cell[i].z>>cell[i].r;
        }
        int es=0;//边的数量
        for(int i=0;i<n;i++){
            for(int j=0;j<i;j++){
                double radius=cell[i].r+cell[j].r;//半径之和
                double distance=sqrt((cell[i].x-cell[j].x)*(cell[i].x-cell[j].x)+(cell[i].y-cell[j].y)*(cell[i].y-cell[j].y)+(cell[i].z-cell[j].z)*(cell[i].z-cell[j].z));
                if(distance<=radius)//重叠
                    edges[es].from=i,edges[es].to=j,edges[es++].w=0.000;
                else{
                    edges[es].from=i,edges[es].to=j,edges[es++].w=distance-radius;
                }
                //cout<<distance<<" ";
            }
            //cout<<endl;
        }
    double end=kruskal(es);
    printf("%.3f\n",end);
    }
    return 0;
}