注意精度问题，不要用强转。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <iostream>
#include <cmath>
#define N 1010
#define INF 0x3f3f3f3f
using namespace std;

int n;
double x[N],y[N];
double dis[N][N];

double d[N];
int vis[N];
bool mp[N][N];
double ans;

struct Edge{
	int v,next;
}edge[N*2];
int head[N],cnt;

double dp[N][N];

void init(){
	memset(head,-1,sizeof(head));
	cnt=0;
}

void addedge(int u,int v){
	edge[cnt].v=v;
	edge[cnt].next=head[u];
	head[u]=cnt++;
	edge[cnt].v=u;
	edge[cnt].next=head[v];
	head[v]=cnt++;
}
double ren[N];

void prim(){
	for(int i=0;i<n;i++){
		vis[i]=0;
		d[i]=dis[0][i];
	}
	vis[0]=-1;
	ans=0;
	memset(mp,0,sizeof(mp));
	for(int i=1;i<n;i++){
		double Min=(double)INF;
		int node=-1;
		for(int j=0;j<n;j++){
			if(vis[j]!=-1 && d[j]<Min){
				node=j;
				Min=d[j];
			}
		}

		ans+=Min;
		mp[vis[node]][node]=mp[node][vis[node]]=1;
		addedge(vis[node],node);
		vis[node]=-1;

		for(int j=0;j<n;j++){
			if(vis[j]!=-1 && d[j]>dis[node][j]){
				vis[j]=node;
				d[j]=dis[node][j];
			}
		}
	}
}
struct node{
	double maxdis;
	int to, fa;
	node(double a=0,int b=0, int c=0):maxdis(a),to(b),fa(c){}
};
void BFS(int x){
	queue<node>q;
	q.push(node(0,x,-1));
	while(!q.empty()){
		node u = q.front(); q.pop();
		for(int i = head[u.to]; ~i; i = edge[i].next){
			int v = edge[i].v; if(v == u.fa)continue;
			double nowmax = max(dis[u.to][v], u.maxdis);
			dp[x][v] = dp[v][x] = max(dp[x][v], nowmax);
			q.push(node(nowmax, v, u.to));
		}
	}
}
int main(){
	int T;  scanf("%d",&T);
	while(T--){
		scanf("%d",&n);
		for(int i=0;i<n;i++)   scanf("%lf %lf %lf",&x[i],&y[i],&ren[i]);

		for(int i=0;i<n;i++)
			for(int j=i;j<n;j++)
				dis[i][j]=dis[j][i]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
		init();
		prim();
		for(int i=0;i<n;i++)
			for(int j=i;j<n;j++)
				dp[i][j]=dp[j][i]=0;
		for(int j=0;j<n;j++) BFS(j);
		double ANS=0;
		for(int i=0;i<n;i++)
			for(int j=i+1;j<n;j++)
				if(mp[i][j])    ANS=max(ANS,(ren[i]+ren[j])/(ans-dis[i][j]));     
				else			ANS=max(ANS,(ren[i]+ren[j])/(ans-dp[i][j]));

				printf("%.2lf\n",ANS);
	}
	return 0;
}
/*
99
4
1 1 20
1 2 30
200 2 80
200 1 100
3
1 1 20
1 2 30
2 2 40 


*/

HDU 4081 秦始皇修路 次小生成树