HDU 4081 Qin Shi Huang's National Road System [次小生成树]

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
#include<math.h>
#define INF 0x3f3f3f3f
using namespace std;
struct city{
    int x,y,p;
};
city jilu[1005];
int n,from[1005];
double dp[1005][1005],dis[1005],total;
bool vis[1005];
double cal(city a,city b){
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
void prim(int pos){
    vis[pos]=1;
    for(int i=0;i<n;i++){
        if(dis[i]>cal(jilu[pos],jilu[i])){
            dis[i]=cal(jilu[pos],jilu[i]);
            from[i]=pos;
        }
    }
    int next=-1;
    double mmin=1e32;
    for(int i=0;i<n;i++){
        if(vis[i]==0&&mmin>dis[i]){
            mmin=dis[i];
            next=i;
        }
    }
    if(next>0){
        for(int i=0;i<n;i++){
            if(vis[i]){
                dp[i][next]=max(dp[i][from[next]],mmin);
            }
        }
        total+=mmin;
        prim(next);
    }
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        for(int i=0;i<n;i++){
            scanf("%d%d%d",&jilu[i].x,&jilu[i].y,&jilu[i].p);
        }
        for(int i=0;i<n;i++){
            dis[i]=1e32;
        }
        memset(dp,0,sizeof(dp));
        memset(vis,0,sizeof(vis));
        total=0;
        prim(0);
        double ans=-1;
        for(int i=0;i<n;i++){
            for(int j=0;j<n;j++){
                if(i!=j){
                    ans=max(ans,(jilu[i].p+jilu[j].p)*1.0/(total-max(dp[i][j],dp[j][i])));
                }
            }
        }
        printf("%.2lf\n",ans);
    }
}