newton.txt

来自「实现牛顿插值多项式的程序源码」· 文本 代码 · 共 49 行

#include<stdio.h>
#define MAX_N 20
typedef struct tagPOINT
{
 double x;
 double y;
}POINT;
int main()
{
 int n;
 int i,j;
 double points[];
  POINT point[MAX_N+1];double diff[MAX_N];
  double x,tmp,newton=0;
  printf("\nInput n value:");
  scanf("%d",&n);
  if(n>MAX_N)
  {
   printf("The input n is larger than MAX_N,please redefine the MAX_N.\n");
   return 1;
  }
  if(n<0)
  {
   printf("Please input a number between 1 and %d.\n",MAX_N);
   return 1;
  }
  printf("Now input the(x_i,y_i),i=0,...,%d:\n",n);
  for(i=0;i<=n;i++)
   scanf("%1f&1f",&points[i].x,points[i].y);
  printf("Now input the x value:");
  scanf("%1f",&x);
  for(i=0;i<=n;i++)
   diff[i]=prints[i].y;
  for(i=0;i<n;i++)
  {
   for(j=n;j>i;j--)
   {
    diff[j]=(diff[j]-diff[j-1])/(prints[j].x-prints[j-1-i].x);
   }
  }
  tmp=1;newton=diff[0];
  for(i=0;i<n;i++)
  {
   tmp=tmp*(x-points[i].x);
   newton=newton+tmp*diff[i+1];
  }
  printf("newton(%f)=%f\n",x,newton);
  return 0;
}