POJ

题目：给定空间的n个点，求最小外接球，输出半径

思路：不知道为什么不管移动后是否最优都要移动，我按照模板上面那样弄就是过不了，一直WA

代码：

#pragma comment(linker, "/STACK:1024000000,1024000000")#include<iostream>#include<algorithm>#include<cstdio>#include<cmath>#include<cstring>#include<string>#include<vector>#include<map>#include<set>#include<queue>#include<stack>#include<list>#include<numeric>using namespace std;#define LL long long#define ULL unsigned long long#define INF 0x3f3f3f3f#define mm(a,b) memset(a,b,sizeof(a))#define PP puts("*********************");template<class T> T f_abs(T a){ return a > 0 ? a : -a; }template<class T> T gcd(T a, T b){ return b ? gcd(b, a%b) : a; }template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}// 0x3f3f3f3f3f3f3f3f// 0x3f3f3f3f#define T_min 1e-8//搜索停止阈值#define delta 0.98//温度下降速度const int maxn=105;struct Node{    double x,y,z;    Node(double _x=0.0,double _y=0.0,double _z=0.0):x(_x),y(_y),z(_z){}}p[maxn];int n;double Dis(Node a,Node 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 get_maxr(Node pos){    double res=0;    for(int i=0;i<n;i++){        res=max(res,Dis(pos,p[i]));    }    return res;}double Search(){    double x=p[0].x,y=p[0].y,z=p[0].z;//随机初始化一个点开始搜索    double T=100000;//初始化温度    double ans=get_maxr(Node(x,y,z));//初始化答案    while(T>T_min){        double dx,dy,dz,mxdis=0;        for(int i=0;i<n;i++){            double dis=Dis(Node(x,y,z),p[i]);            if(dis>mxdis){                mxdis=dis;                dx=(p[i].x-x)/dis;                dy=(p[i].y-y)/dis;                dz=(p[i].z-z)/dis;            }        }        double cur=get_maxr(Node(x+T*dx,y+T*dy,z+T*dz));        if(cur<=ans){            ans=cur;        }            x=x+T*dx;            y=y+T*dy;            z=z+T*dz;//        }//        else if(exp((cur-ans)/T)<rand()/(RAND_MAX+1.0)){//            ans=cur;//            x=x+T*dx;//            y=y+T*dy;//            z=z+T*dz;//        }        T=T*delta;    }    return ans;}int main(){    while(~scanf("%d",&n)){        if(!n) break;        for(int i=0;i<n;i++)            scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].z);        double ans=Search();        printf("%.5f\n",ans);    }    return 0;}