lagrange.cpp

来自「用C++实现的多个算法」· C++ 代码 · 共 24 行

#include<iostream.h>

float Lagrange(float x)      
{
	float x1[]={-1,0,1,2}, y1[]={1,1,1,-1};
	int n=(sizeof(x1)/sizeof(int))-1;
	float y,t;
	int k,j;
	y=0;
	for(k=0;k<=n;k++)
	{
		t=1;
		for(j=0;j<=n;j++)
			if(j!=k)
				t=t*((x-x1[j])/(x1[k]-x1[j]));
			y=y+t*y1[k];
	}
	return y;
}
void main()
{
	cout<<" "<<Lagrange(0.5)<<endl;
}