龙贝格.cpp

龙贝格算法,一个数值分析中的算法,大家先看看吧,有问题及时改正

# include <iostream.h>
# include <math.h>
double f(double n)
{
	double a=sin(n);
	double b=a/n;
	return b;
}
void main ()
{
	double a,b,c,s,h,x,t1,t2,c1,c2,r1,r2,s1,s2;
	cout<<"Please put into three numbers:\n";
	cin>>a>>b>>c;
	int k=1,i=1,j=0;
	h=b-a;
	t1=(f(a)+f(b))*h/2;
	while (i)
	{
		if (j==1)
		{
			k=k+1;
			h=h/2;
			t1=t2;
			s1=s2;
		}
		j=0;
		s=0;
		x=a+h/2;
		while (x<b)
		{
			s=s+f(x);
			x=x+h;
		}
		t2=t1/2+h*s/2;
		s2=t2+(t2-t1)/3;
		if (k==1)
		{
			j=1;
			continue;
		}
		else 
		{
			c2=s2+(s2-s1)/15;
			if (k==2)
			{
				c1=c2;
				j=1;
				continue;
			}
			else 
			{
				r2=c2+(c2-c1)/63;
				if (k==3)
				{
					r1=r2;
					c1=c2;
					j=1;
					continue;
				}
				else 
                if (r2-r1<c && r1-r2<c)
					{
						cout<<r2<<endl;
						i=0;
					}
					else 
					{
					    r1=r2;
						c1=c2;
						j=1;
						continue;
					}
			}
		}
	}
}