最小圆覆盖板子

int sgn(double x) {
	if(fabs(x) < eps)return 0;
	else return x<0?-1:1;
};
struct Point {double x,y;};
double Distance(Point A,Point B) {return hypot(A.x-B.x,A.y-B.y);}

//三角形外接圆圆心
Point circle_center(const Point a,const Point b,const Point c) {
	Point center;
	double a1=b.x-a.x,b1=b.y-a.y,c1=(a1*a1+b1*b1)/2;
	double a2=c.x-a.x,b2=c.y-a.y,c2=(a2*a2+b2*b2)/2;
	double d = a1*b2-a2*b1;
	center.x = a.x+(c1*b2-c2*b1)/d;
	center.y = a.y+(a1*c2-a2*c1)/d;
	return center;
}

void min_cover_circle(Point *p,int n,Point &c,double &r) {
	random_shuffle(p,p+n);
	c=p[0];
	r=0;
	for(int i=1; i<n; i++) {
		if(sgn(Distance(p[i],c)-r)>0) {  //p[i]在圆外
			c = p[i];
			r=0;
			for(int j=0; j<i; j++) {
				if(sgn(Distance(p[j],c)-r)>0) {
					c.x = (p[i].x + p[j].x) / 2;
					c.y = (p[i].y + p[j].y) / 2;
					r = Distance(p[j],c);
					for(int k=0; k<j; k++) {
						if(sgn(Distance(p[k],c)-r ) > 0) {
							c = circle_center(p[i],p[j],p[k]);
							r=Distance(p[i],c);
						}
					}
				}
			}
		}
	}
}
int n;
Point p[N];
Point c;
double r;

void work() {
	while(~scanf("%d",&n) && n) {
		for(int i=0; i<n; i++) {
			scanf("%lf%lf",&p[i].x,&p[i].y);
		}
		min_cover_circle(p,n,c,r);
		printf("%.2f %.2f %.2f
",c.x,c.y,r);
	}
}