/*該程序功能：改進歐拉格式，據101頁流程圖。*/
                          #include "stdafx.h"
                             #include<stdio.h>
                                #include<iostream.h>
double f(double x0,double y0)
{
	double y;
	    y=y0-2*x0/y0;
	          return y;
}
void imp(double x0,double y0,double h,int N)
{
 int n,flag;
   double x1,y1,yp,yc;
     n=1,flag=0;
 cout<<"Now the result is:"<<endl;
   cout<<" xn       yn    "<<endl;
  do{
	  if(flag)
	  {
		n+=1;
		 x0=x1;
		  y0=y1;
	  }
	   x1=x0+h;
	     yp=y0+h*f(x0,y0);
	       yc=y0+h*f(x1,yp);
	         y1=(yp+yc)/2;
	   printf(" %.1f    %.4f\n",x1,y1);
	        flag=1;
  }while(n!=N);
}
int main(int argc, char* argv[])
{
	int N;
 double x0,y0,h;
  cout<<"Please enter x0=";
    cin>>x0;
  cout<<"Please enter y0=";
    cin>>y0;
  cout<<"please enter h=";
     cin>>h;
cout<<"please enter N=";
     cin>>N;		 
  imp(x0,y0,h,N);	
	return 0;
}