优化方法——0.618法（黄金分割法）

#include 
using namespace std;
//0.618法
class Solution
{
public:
	Solution(double x, double y) :a(x), b(y)
	{
		cout << "init parameter successn";
	}
	double func(double& x) const//计算函数值
	{
		return x*(x + 2);
	}
	double solve(double lamda, double dif)
	{
		while (b - a > dif)
		{
			x1 = b - lamda*(b - a);
			x2 = a + lamda*(b - a);
			f1 = func(x1);
			f2 = func(x2);
			if (f1 > f2)
			{
				a = x1;
				x1 = x2;
				f1 = f2;
				x2 = a + lamda*(b - a);
				f2 = func(x2);
			}
			else
			{
				b = x2;
				x2 = x1;
				f2 = f1;
				x1 = b - lamda*(b - a);
				f1 = func(x1);
			}
		}
		res = 0.5*(b + a);
		return func(res);
	}
private:
	double a;
	double b;
	double x1;
	double x2;
	double f1;
	double f2;
	double res;
};

int main()
{
	Solution sol(-4, 6);
	
	cout << sol.solve(0.618, 0.3);
	system("pause");
	return 0;
}