#include <stdio.h>
#include <math.h>

double pl[30][3];
double formula[3][4];

inline double dim2(int a,int b)
{
	double x=(pl[a][0]+pl[b][0])/2,y=(pl[a][1]+pl[b][1])/2,z=(pl[a][2]+pl[b][2])/2;
	double ret=(x-pl[a][0])*(x-pl[a][0])+(y-pl[a][1])*(y-pl[a][1])+(z-pl[a][2])*(z-pl[a][2]);
	if(fabs(ret)<1e-7)
		return -1;
	else
		return ret;
}

inline double fdet3(int a,int b,int c)
{
	return formula[0][a]*formula[1][b]*formula[2][c]
		+formula[0][b]*formula[1][c]*formula[2][a]
		+formula[0][c]*formula[1][a]*formula[2][b]
		-formula[0][c]*formula[1][b]*formula[2][a]
		-formula[0][a]*formula[1][c]*formula[2][b]
		-formula[0][b]*formula[1][a]*formula[2][c];
}

inline bool solve3(double &x,double &y,double &z)
{
	double comm=fdet3(0,1,2);
	if(fabs(comm)<1e-7)
		return false;
	x=fdet3(3,1,2)/comm;
	y=fdet3(0,3,2)/comm;
	z=fdet3(0,1,3)/comm;
	return true;
}

inline double dim3(int a,int b,int c)
{
	int i;
	formula[0][3]=0; formula[1][3]=0; formula[2][3]=0;
	for(i=0;i<3;i++)
	{
		formula[0][i]=pl[a][i]-pl[b][i];
		formula[1][i]=pl[a][i]-pl[c][i];
		formula[0][3]+=formula[0][i]*(pl[a][i]+pl[b][i])/2;
		formula[1][3]+=formula[1][i]*(pl[a][i]+pl[c][i])/2;
	}
	double sl=0.0;
	formula[2][0]=formula[0][1]*formula[1][2]-formula[0][2]*formula[1][1];
	formula[2][1]=-formula[0][0]*formula[1][2]+formula[0][2]*formula[1][0];
	formula[2][2]=formula[0][0]*formula[1][1]-formula[0][1]*formula[1][0];
	if(fabs(formula[2][0])<1e-7 && fabs(formula[2][1])<1e-7 && fabs(formula[2][2])<1e-7)
		return -1;
	for(i=0;i<3;i++)
		formula[2][3]+=formula[2][i]*pl[a][i];
	double x,y,z;
	if(solve3(x,y,z))
		return (x-pl[a][0])*(x-pl[a][0])+(y-pl[a][1])*(y-pl[a][1])+(z-pl[a][2])*(z-pl[a][2]);
	else
		return -1;
}

inline double dim4(int a,int b,int c,int d)
{
	int i;
	formula[0][3]=0; formula[1][3]=0; formula[2][3]=0;
	for(i=0;i<3;i++)
	{
		formula[0][i]=pl[a][i]-pl[b][i];
		formula[1][i]=pl[a][i]-pl[c][i];
		formula[2][i]=pl[a][i]-pl[d][i];
		formula[0][3]+=formula[0][i]*(pl[a][i]+pl[b][i])/2;
		formula[1][3]+=formula[1][i]*(pl[a][i]+pl[c][i])/2;
		formula[2][3]+=formula[2][i]*(pl[a][i]+pl[d][i])/2;
	}
	double x,y,z;
	if(solve3(x,y,z))
		return (x-pl[a][0])*(x-pl[a][0])+(y-pl[a][1])*(y-pl[a][1])+(z-pl[a][2])*(z-pl[a][2]);
	else
		return -1;
}

int main()
{
	int n;
	while(scanf("%d",&n),n)
	{
		int i,j,k,l;
		double max=-1,temp;
		for(i=0;i<n;i++)
			for(j=0;j<3;j++)
				scanf("%lf",&pl[i][j]);
		for(i=0;i<n;i++)
			for(j=i+1;j<n;j++)
			{
				temp=dim2(i,j);
				if(temp>max)
					max=temp;
			}
		for(i=0;i<n;i++)
			for(j=i+1;j<n;j++)
				for(k=j+1;k<n;k++)
				{
					temp=dim3(i,j,k);
					if(temp>max)
						max=temp;
				}
		for(i=0;i<n;i++)
			for(j=i+1;j<n;j++)
				for(k=j+1;k<n;k++)
					for(l=k+1;l<n;l++)
					{
						temp=dim4(i,j,k,l);
						if(temp>max)
							max=temp;
					}
		printf("%0.5lf\n",sqrt(max)+1e-7);
	}
	return 0;
}

• Re:Why wa? I've been trying on tihs for several days... (16) szwj 2008-03-05 17:22:14
• Re:Why wa? I've been trying on tihs for several days... (3207) Jarviszhang 2019-06-18 16:55:14