G

G - Arctic Network

 

#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define MAXN 510
using namespace std;
double an;
int fa[MAXN];
int t,n,m,tot,sum;
double x[MAXN],y[MAXN],ans[MAXN];
struct nond{
    int x,y;double z;
}v[MAXN*MAXN];
int cmp(nond a,nond b){
    return a.z<b.z;
}
int find(int x){
    if(fa[x]==x)    return x;
    else  return fa[x]=find(fa[x]);
}
int main(){
    scanf("%d",&t);
    while(t--){
        an=0;sum=0;tot=0;
        scanf("%d%d",&n,&m);
        for(int i=1;i<=m;i++)
            scanf("%lf%lf",&x[i],&y[i]);
        for(int i=1;i<=m;i++)
            for(int j=i+1;j<=m;j++){
                double tmp=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
                v[++tot].x=i;v[tot].y=j;v[tot].z=tmp;
            }
        for(int i=1;i<=m;i++)    fa[i]=i;
        sort(v+1,v+1+tot,cmp);
        for(int i=1;i<=tot;i++){
            int dx=find(v[i].x);
            int dy=find(v[i].y);
            if(dx==dy)    continue;
            fa[dy]=dx;
            ans[++sum]=v[i].z;
            if(sum==m-1)    break;
        }
        for(int i=1;i<=m-n;i++)
            an=max(an,ans[i]);
        printf("%.2lf
",an);
    }
}