4081 Qin Shi Huang's National Road System

#include<cstdio>
#include<cstring>
#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
#define maxn 1100
#define maxm 2200
#define INF 1100000
struct Point
{
    double x,y,w;
}p[maxn];
struct Edge
{
    int s,e;
    double len;
}e[maxn*maxn];
int n,m;
double tolen;
double maxLen[maxn][maxn];
int father[maxn];
int head[maxn],v[maxm],next[maxm],cnt;
double w[maxm];
int vis[maxn];

void init()
{
    memset(head,-1,sizeof(head));
    memset(father,-1,sizeof(father));
    memset(maxLen,0,sizeof(maxLen));
    cnt=0;
}
double Dis(int a,int b)
{
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)
               +(p[a].y-p[b].y)*(p[a].y-p[b].y));
}
void add(int a,int b,double c)
{
    v[cnt]=b;
    w[cnt]=c;
    next[cnt]=head[a];
    head[a]=cnt++;
}
bool cmp(Edge a,Edge b)
{
    return a.len<b.len;
}
int getFather(int i)
{
    if(father[i]==-1)
        return i;
    return father[i]=getFather(father[i]);
}
void kru()
{
    init();
    sort(e+1,e+1+m,cmp);
    tolen=0.0;
    int num=0;
    for(int i=1;i<=m;i++)
    {
        int a=getFather(e[i].s);
        int b=getFather(e[i].e);
        if(a!=b)
        {
            num++;
            father[a]=b;
            tolen+=e[i].len;
            add(e[i].s,e[i].e,e[i].len);
            add(e[i].e,e[i].s,e[i].len);
        }
        if(num==n-1)
            break;
    }
}
void dfs(int u,int x)
{
    for(int i=head[x];~i;i=next[i])
        if(!vis[v[i]])
        {
            vis[v[i]]=1;
            maxLen[u][v[i]]=max(maxLen[u][x],Dis(x,v[i]));
            dfs(u,v[i]);
        }
}
void solve(int u)
{
    memset(vis,0,sizeof(vis));
    vis[u]=1;
    dfs(u,u);
}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        cin>>n;
        for(int i=1; i<=n; i++)
            scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].w);
        m=0;
        for(int i=1;i<=n;i++)
        {
            for(int j=i+1;j<=n;j++)
            {
                m++;
                e[m].s=i;
                e[m].e=j;
                e[m].len=Dis(i,j);
            }
        }
        kru();
        for(int i=1; i<=n; i++)
            solve(i);
        double pi=0.0;
        for(int i=1; i<=n; i++)
        {
            double tmp;
            for(int j=i+1; j<=n; j++)
            {
                tmp=p[i].w+p[j].w;
                pi=max(pi,tmp/(tolen-maxLen[i][j]));
            }
        }
        printf("%.2lf\n",pi);
    }
    return 0;
}