lagrangeczf.cpp

计算方法计算方法程序lagelangrichazhi 拉格朗日插值法.rar

#include<iostream.h>

void lagranechzhi();

int main()
{
	lagranechzhi();
	return 0;
}

void lagranechzhi()
{
	int N;
	cout<<"请输入要插入点的个数:";
	cin>>N;
	double x,y=0;
	double*a,*b;
	a=new double[N];
	b=new double[N];

	for(int k=0;k<N;k++)
	{
		cout<<"第"<<k+1<<"个点的坐标为:";
		cin>>a[k]>>b[k];
	}
	cout<<"请输入要计算的数:";
	cin>>x;
	for(int i=0;i<N;i++)
	{
		double p=1;
		for(int j=0;j<N;j++)
		{
			if(i==j) continue;
			p=p*(x-a[j])/(a[i]-a[j]);
		}
		y=y+p*b[i];
	}
	cout<<"==============\n"<<"f("<<x<<")="<<y<<endl;
	delete[]a;
	delete[]b;
}