lagelangri.cpp

数值计算方法中的知识

#include<iostream.h>
#define M 100
void main()
{
	int n,i,k,j,m=1;
	float u,v,t,x[M],y[M]; 
	cout<<"y=1/(1+x*x)  (-2<=x<=2)用lagrange插值函数作近似,将[-2，2]的等分点作为插值点"<<endl<<endl;
	do
	{
	cout<<"请输入插值点个数:";
    cin>>n;
    cout<<"请输入插值结点:";
	for(i=0;i<=n;i++)
	{
		cin>>x[i];
		y[i]=1/(1+x[i]*x[i]);
	}
    cout<<"请输入插值点:";
	cin>>u; 
	v=0;
	for(k=0;k<=n;k=k+1)
	{
		t=1;
		for(j=0;j<=n;j=j+1)
		{
			if(j!=k)
			{
				t=t*((u-x[j])/(x[k]-x[j]));
			}
		}
		v=v+t*y[k];
	}
	cout<<"近似值:"<<v<<endl<<endl;
	}while(m=1);
}