luogu1742 最小圆覆盖

狗题卡我精度……sol

#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <ctime>
#include <cmath>
using namespace std;
int n;
struct Point{
	double x, y;
}pt[100005], O;
double r;
const double eps=1e-10;
double dis(const Point &u, const Point &v){
	return sqrt((u.x-v.x)*(u.x-v.x)+(u.y-v.y)*(u.y-v.y));
}
void getO(const Point &u, const Point &v, const Point &w){
	double a=u.x-v.x;
	double b=u.y-v.y;
	double c=v.x-w.x;
	double d=v.y-w.y;
	double e=a*(u.x+v.x)+b*(u.y+v.y);
	double f=c*(v.x+w.x)+d*(v.y+w.y);
	O.x = (e*d-b*f)/(a*d-c*b)/2;
	O.y = (c*e-a*f)/(b*c-a*d)/2;
}
bool inCircle(const Point &u){
	return dis(u,O)<=r+eps;
}
int main(){
	srand(time(NULL));
	cin>>n;
	for(int i=1; i<=n; i++)
		scanf("%lf %lf", &pt[i].x, &pt[i].y);
	random_shuffle(pt+1, pt+1+n);
	O = pt[1];
	for(int i=1; i<=n; i++)
		if(!inCircle(pt[i])){
			O = pt[i];
			for(int j=1; j<i; j++)
				if(!inCircle(pt[j])){
					O = (Point){(pt[i].x+pt[j].x)/2, (pt[i].y+pt[j].y)/2};
					r = dis(pt[i], pt[j]) / 2.0;
					for(int k=1; k<j; k++)
						if(!inCircle(pt[k])){
							getO(pt[i], pt[j], pt[k]);
							r = dis(O, pt[k]);
						}
				}
		}
	printf("%.10f\n%.10f %.10f\n", r, O.x, O.y);
	return 0;
}