half.cpp

二分法方程求根的经典算法

#include<iostream.h>
double fot(double a,double b,double eps);
double f(double x);
void main()
{
	double a,b,eps;
	cout<<"方程的区间下限a=";
	cin>>a;
	cout<<"方程的区间上限b=";
	cin>>b;
	cout<<"要求误差eps:";
	cin>>eps;
	cout<<"方程所求根为:"<<fot(a,b,eps)<<endl;
}
double f(double x)
{
	double y;
    y=x*x*x-x-1;
	
	return y;
}
double fot(double a,double b,double eps)
{
	double x,y,y0;
	do
	{
		y0=f(a);
		x=(a+b)/2.0;
		y=f(x);
		if(y*y0>0)
			a=x;
		else
			b=x;
	}while((b-a)>eps);
	return x;
}