题意为求点的最小外接球。
本想随机模拟退火，可是怎么也掌握不好火候。
后来改为每次定向变步长，取的点向离它最远的那个点移动。
初始随机了10个点。

POJ 2069
#include<iostream>
#include<time.h>
#include<cmath>
#define sqr(x) (x)*(x)
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define FF(i,a) for(int i=0;i<a;i++)
using namespace std;
const double eps=1e-6;
const double INF=1e20;
const double pi=acos(-1.0);
struct Houxuan
{
    double x,y,z,dist;
}pp[10];
struct PT
{
    double x,y,z;
}hole[30];
double dis(double x1,double y1,double z1,double x2,double y2,double z2)
{
    return sqrt(sqr(x1-x2)+sqr(y1-y2)+sqr(z1-z2));
}
int n;
int main()
{
    int P=10;
    while(scanf("%d",&n)&&n)
    {
        double delta=100.0;
        FF(i,n)
            scanf("%lf%lf%lf",&hole[i].x,&hole[i].y,&hole[i].z);
        FF(i,P)
        {
            pp[i].x=double(rand()%10000+1)/10000.0*100;
            pp[i].y=double(rand()%10000+1)/10000.0*100;
            pp[i].z=double(rand()%10000+1)/10000.0*100;
            pp[i].dist=0;
            FF(j,n)
                pp[i].dist=max(pp[i].dist,dis(pp[i].x,pp[i].y,pp[i].z,hole[j].x,hole[j].y,hole[j].z));
        }
        while(delta>eps)
        {
            FF(i,P)
            {
                int idx=0;
                double tmp=0;
                FF(j,n)
                {
                    double d=dis(hole[j].x,hole[j].y,hole[j].z,pp[i].x,pp[i].y,pp[i].z);
                    if(d>tmp)
                    {
                        idx=j;
                        tmp=d;
                    }
                }
                pp[i].dist=min(pp[i].dist,tmp);
                pp[i].x=pp[i].x+(hole[idx].x-pp[i].x)/tmp*delta;
                pp[i].y=pp[i].y+(hole[idx].y-pp[i].y)/tmp*delta;
                pp[i].z=pp[i].z+(hole[idx].z-pp[i].z)/tmp*delta;
            }
            delta*=0.98;
        }
        int idx=0;
        FOR(i,1,P)
        {
            if(pp[i].dist<pp[idx].dist)
                idx=i;
        }    
        printf("%.5lf\n",pp[idx].dist);    
    }
    return 0;
}