六顿差商.cpp

这是计算方法上的所有算法

#include<stdio.h>
#include<conio.h>
#define N 4
static double x[N+1]={0.4,0.55,0.8,0.9,1};
static double y[N+1]={0.41075,0.57815,0.88811,1.02652,1.17520};
int checkvalid(double x[],int n)
{
	int i,j,flag=1;
	for(i=0;i<n;i++)
	for(j=i+1;j<n;j++)
		if(x[i]==x[j])

		{flag=0;
		break;
	}
	return flag;
}
void chashang (double x[],double y[],double  f[][N+1])
{
	int i,j,n=1;
	double a,b;
	for(i=0;i<=N;i++)
		f[0][i]=y[i];
	for(i=0;i<N;i++)
	{	for(j=0;j<=N-n;j++)
		{
			a=f[i][j];
			b=f[i][j+1];
			f[i+1][j]=(b-a)/(x[j+n]-x[j]);
		}
	n++;
	}
}
double compvalue(double t[][N+1],double x[],double varx)
{
	double c,r=0.0,s=0.0;int i,j;
	c=t[0][0];
	
	for(j=0;j<=N;j++)
	{c=1.0;
	    i=0;
		while(i<j)
		{c*=(varx-x[i]);
		i++;
		}
		r=c*t[j][0];
		s+=r;
	}
	printf("\n");
	return s;
}
void main()
{
	double varx,f[N+1][N+1];

	varx=0.5;
	if(checkvalid(x,N)==1)
	{
		chashang(x,y,f);
		printf("\nP(%f)=%f",varx,compvalue(f,x,varx));
	}else printf("");
}