HDU 5017アナログアニーリングアルゴリズム

#include <bits/stdc++.h>
using namespace std;
const int MOD = 1E9 + 7;
const double eps = 1E-8;
int dx[8] = {0, 0, 1, -1, 1, -1, 1, -1};
int dy[8] = {1, -1, 0, 0, 1, 1, -1, -1};
double a, b, c, d, e, f;
double dis(double x, double y, double z)
{
	return sqrt(x * x + y * y + z * z);//    
}
double calc(double x, double y)// x，y  z 
{
	double A = c;
	double B = d * y + e * x;
	double C = f * x * y + a * x * x + b * y * y - 1.0;
	double delta = B * B - 4.0 * A * C;//        
	if (delta < 0.0)return MOD + 10.0;//    x，y      
	delta = sqrt(delta);//   
	double soz1 = (-B + delta) / (2.0 * A);
	double soz2 = (-B - delta) / (2.0 * A);
	if (dis(x, y, soz1) < dis(x, y, soz2))
		return soz1;
	return soz2;//        z 
}
double Simulated_Annealing()
{
	double x = 0, y = 0, z = sqrt(1.0 / c);// z         
	double step = 1.0, rate = 0.99;
	while (step > eps)//    0，       
	{
		for (int k = 0; k < 8; k++)//          
		{
			double kx = x + step * dx[k];//    step   
			double ky = y + step * dy[k];
			double kz = calc(kx, ky);
			if (kz >= MOD) continue;//  x，y，    
			if (dis(kx, ky, kz) < dis(x, y, z))
				x = kx, y = ky, z = kz;//  
		}
		step *= rate;//     rate     ，      
	}
	return dis(x, y, z);//    
}
int main(int argc, char const *argv[])
{
	while (cin >> a >> b >> c >> d >> e >> f)
		cout << setprecision(7) << fixed << Simulated_Annealing() << endl;
	return 0;
}

注釈を読む
参考資料:http://www.cnblogs.com/heaad/archive/2010/12/20/1911614.html
http://www.cnblogs.com/whatbeg/p/3975624.html

#include <bits/stdc++.h>
using namespace std;
const int MOD = 1E9 + 7;
const double eps = 1E-8;
int dx[8] = {0, 0, 1, -1, 1, -1, 1, -1};
int dy[8] = {1, -1, 0, 0, 1, 1, -1, -1};
double a, b, c, d, e, f;
double dis(double x, double y, double z)
{
	return sqrt(x * x + y * y + z * z);
}
double calc(double x, double y)
{
	double A = c;
	double B = d * y + e * x;
	double C = f * x * y + a * x * x + b * y * y - 1.0;
	double delta = B * B - 4.0 * A * C;
	if (delta < 0.0)return MOD + 10.0;
	delta = sqrt(delta);
	double soz1 = (-B + delta) / (2.0 * A);
	double soz2 = (-B - delta) / (2.0 * A);
	return (dis(x, y, soz1) < dis(x, y, soz2) ? soz1 : soz2);
}
double Simulated_Annealing()
{
	double x = 0, y = 0, z = sqrt(1.0 / c);
	for (double step = 1.0, rate = 0.99; step > eps; step *= rate)//        
		for (int k = 0; k < 8; k++)
		{
			double kx = x + step * dx[k];
			double ky = y + step * dy[k];
			double kz = calc(kx, ky);
			if (kz >= MOD) continue;
			if (dis(kx, ky, kz) < dis(x, y, z))
				x = kx, y = ky, z = kz;
		}
	return dis(x, y, z);
}
int main(int argc, char const *argv[])
{
	while (cin >> a >> b >> c >> d >> e >> f)
		cout << setprecision(7) << fixed << Simulated_Annealing() << endl;
	return 0;
}