【Country Meow】2018ICPC南京D题

1.emm，最小球覆盖的裸题，直接模拟退火。。

#include<bits/stdc++.h>
using namespace std;
#pragma warning(disable:4996)
const double eps = 1e-8;
struct point3D
{
	double x, y, z;
} p[105];
int n;
double dis(point3D a, point3D 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 solve()
{
	double step = 10000, ans = 1e30, mt;
	point3D z;
	z.x = z.y = z.z = 0;
	int s = 0;
	while (step > eps)
	{
		for (int i = 0; i < n; i++)
			if (dis(z, p[s]) < dis(z, p[i]))
				s = i;
		mt = dis(z, p[s]);
		ans = min(ans, mt);
		z.x += (p[s].x - z.x) / mt * step;
		z.y += (p[s].y - z.y) / mt * step;
		z.z += (p[s].z - z.z) / mt * step;
		step *= 0.98;
	}
	return ans;
}
int main()
{
	double ans;
	while (scanf("%d", &n) != EOF)
	{
		for (int i = 0; i < n; i++)
			scanf("%lf%lf%lf", &p[i].x, &p[i].y, &p[i].z);
		ans = solve();
		printf("%.7f\n", ans);
	}
	return 0;
}