模拟退火。
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define maxn 30
#define eps 1e-7
using namespace std;
struct point
{
double x,y,z;
}p[maxn],s;
int n;
double delta=0.98;
double dist(point a,point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z));
}
double solve()
{
s.x=s.y=s.z=;
int regis=;
double ans=1e30,t=;
while (t>eps)
{
for (int i=;i<=n;i++)
if (dist(s,p[i])>dist(s,p[regis]))
regis=i;
double mt=dist(s,p[regis]);
ans=min(ans,mt);
s.x+=(p[regis].x-s.x)/mt*t;
s.y+=(p[regis].y-s.y)/mt*t;
s.z+=(p[regis].z-s.z)/mt*t;
t*=delta;
}
return ans;
}
int main()
{
for (;;)
{
scanf("%d",&n);
if (n==) break;
for (int i=;i<=n;i++)
scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].z);
printf("%.5lf\n",solve());
}
return ;
}