largreance插值.cpp

largreance插值 迭代法 迭代改善法

#include <stdio.h>
#include<math.h>
#define N 10
void main()
{
	int n,k,i;
	float u,v,X[N+1],Y[N+1];
	printf("请输入n（结点个数减1）");
	scanf("%d",&n);
	printf("请输入插值结点u=");
	scanf("%f",&u);
	for(i=0;i<=n;i++)
	{ printf("请输入结点值X[%d]=",i);
	  scanf("%f",&X[i]);
	  printf("请输入函数值Y[%d]=",i);
	  scanf("%f",&Y[i]);
    }
	for(i=0;i<=n;i++)
	{
    	printf("X[%d]=%f\n",i,X[i]);
		printf("Y[%d]=%f\n",i,Y[i]);
	}
	if(u<=X[0])
	{	k=0;
		v=Y[k]*(u-X[k+1])/(X[k]-X[k+1])+Y[k+1]*(u-X[k])/(X[k+1]-X[k]);
	}
		else 
		  if(u>=X[n])
		  {	   k=n-1;
                v=Y[k]*(u-X[k+1])/(X[k]-X[k+1])+Y[k+1]*(u-X[k])/(X[k+1]-X[k]);
		  }
		    else 
			{	for(i=0;i<n;i++)
					if(u>=X[i]&&u<=X[i+1])
				     k=i;
				
			 v=Y[k]*(u-X[k+1])/(X[k]-X[k+1])+Y[k+1]*(u-X[k])/(X[k+1]-X[k]);  
			}
	 printf("v=%f\n",v);
}