6_12.cpp

使用二分法逼近求函数近似值的c++实现 是数值算法中的基本算法

#include<iostream.h>
#include<math.h>
#define N 100000
double f(double x)
{
	return(3*x+sin(x)-exp(x));
}
double twoPart(double a,double b,double e)
{
	double an=a;
	double bn=b;
	double tn;
	for(int i=0;(f(tn)!=0)&&(fabs((an-bn))>e)&&(i<N);i++)
	{
       tn=(an+bn)/2;
	   if(f(an)*f(tn)<0)
		   bn=tn;
	   else if(f(bn)*f(tn)<0)
		   an=tn;

	}
	if(i>=N)
	{
		cout<<"Can not find!"<<endl;

		return 0;
	}
			
    return tn;

}

void main()
{
   double t;
   if(t=twoPart(0,0.5,0.000001))
   {
	   cout<<"f(x)=0:x="<<t<<endl;
	   cout<<f(t)<<endl;

   }

}