黄金分割法.cpp

一个黄金分割法求最优区间

#include<iostream.h>
#include<math.h>
double f(double x)
{
	double y=x*x-4*x+12;
	return y;
}
void main(void)
{
	double a0,b0,data,a,b,x1,x2;
	cout<<"请输入已知区间及给定精度:\n";
	cin>>a0>>b0>>data;
	a=a0; b=b0;
	while((fabs(b-a)/(b0-a0))>data)
	{
		x1=a+0.618*(b-a);
		x2=b-0.618*(b-a);
		if(f(x1)>=f(x2))
		{
			b=x1; x1=x2;
			x2=b-0.618*(b-a);
		}
		else
		{
			a=x2; x2=x1;
			x1=a+0.618*(b-a);
		}
	}
	if(f(x1)>=f(x2))
	{
		cout<<"最小点坐标为[x2,f2]="<<"["<<x2<<","<<f(x2)<<"]"<<'\n';
		cout<<"最小区间[a,x1]="<<"["<<a<<","<<x1<<"]"<<'\n';
	}
	else
	{
        cout<<"最小点坐标为[x1,f1]="<<"["<<x1<<","<<f(x1)<<"]"<<'\n';
		cout<<"最小区间[x2,b]="<<"["<<x2<<","<<b<<"]"<<'\n';
	}
}