niudun.cpp

数值分析当中牛顿算法

#include<iostream.h>
#include<stdio.h>
#include<math.h>
//#define f(x) (x*x*x-7.7*x*x+19.2*x-15.3)
//#define g(x) (3*x*x-15.4*x+19.2)
#define f(x) (x*x*x-2*x*x-4*x-7)
#define g(x) (3*x*x-4*x-4)
#define x0 0.0
#define x1 1.0
#define MAXREPT 1e4
void main()
{
int i;
double epsilon;
double x_k=x0,x_k1=x1,x_k2=x1;
cout<<"请输入求解精度：";
cin>>epsilon;
    cout<<"迭代开始："<<endl;   
for(i=0;i<MAXREPT;i++)
{
   cout<<"Got..."<<x_k2<<endl;
   x_k2=x_k1-f(x_k1)/g(x_k1);
   if(fabs(x_k2-x_k1)<epsilon)
   {
   cout<<"所得满足精度的解为："<<endl;
   cout<<"!Root="<<x_k2<<endl;
    return;
   }
   x_k=x_k1;x_k1=x_k2;
}
   cout<<"经过 "<<MAXREPT<<" 次迭代后,未达到所需精度要求"<<endl;
}