HDU 1875 畅通工程再续

传送门：http://acm.hdu.edu.cn/showproblem.php?pid=1875

简单的最小生成树

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

const int maxn=10000+5;
const double INF=1.0e20;

struct Node{
    double x,y;
} isl[maxn];

bool book[maxn];
double dis[maxn];

double dist(double x1,double y1,double x2,double y2){
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

int main(){
    int T;
    scanf("%d",&T);
    while(T--){
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;i++){
            scanf("%lf%lf",&isl[i].x,&isl[i].y);
        }

        for(int i=1;i<=n;i++){
            dis[i]=INF;
            book[i]=false;
        }


        dis[1]=0;
        for(int k=1;k<=n;k++){
            int m=-1;
            double mx=INF;

            for(int i=1;i<=n;i++){
                if(!book[i]&&dis[i]<mx){
                    m=i;
                    mx=dis[i];
                }
                }
             
            if(m==-1)
                continue;
                
                book[m]=true;

                for(int i=1;i<=n;i++){
                    if(!book[i]){
                        double d=dist(isl[m].x,isl[m].y,isl[i].x,isl[i].y);

                        if(d>=10.000000&&d<=1000.000001){
                            if(d<dis[i]){
                            dis[i]=d;
                        }
                        }


                    }
                }
            
        }

        double ans=0;
        for(int i=1;i<=n;i++){
            ans+=dis[i];
            if(ans>=INF)
                break;
        }
        int flag=0;
        for(int i=1;i<=n;i++){
            if(book[i]==false){
                flag=1;
                break;
            }
        }
        if(ans>=INF||flag==1){
            printf("oh!\n");
        }
        else{

            printf("%.1lf\n",ans*100);
        }
    }
    return 0;
}