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| #include <iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#define eps 1e-7
#define MS 50
using namespace std;
int n,m;
struct point3D {
double x,y,z;
} data[MS];
double dis(point3D a,point3D 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() {
double step=100,ans=1e30,mt;
point3D z;
z.x=z.y=z.z=0;
int s=0;
while(step>eps) {
for(int i=0; i<n; i++)
if(dis(z,data[s])<dis(z,data[i])) s=i;
mt=dis(z,data[s]);
ans=min(ans,mt);
z.x+=(data[s].x-z.x)/mt*step;
z.y+=(data[s].y-z.y)/mt*step;
z.z+=(data[s].z-z.z)/mt*step;
step*=0.98;
}
return ans;
}
int main() {
double ans;
while(~scanf("%d",&n),n) {
for(int i=0; i<n; i++)
scanf("%lf%lf%lf",&data[i].x,&data[i].y,&data[i].z);
ans=solve();
printf("%.5f\n",ans);
}
return 0;
}
|
