#include <math.h>#define NRANSI#include "nrutil.h"void polint(float xa[], float ya[], int n, float x, float *y, float *dy){	int i,m,ns=1;	float den,dif,dift,ho,hp,w;	float *c,*d;	dif=fabs(x-xa[1]);	c=vector(1,n);	d=vector(1,n);	for (i=1;i<=n;i++) {		if ( (dift=fabs(x-xa[i])) < dif) {			ns=i;			dif=dift;		}		c[i]=ya[i];		d[i]=ya[i];	}	*y=ya[ns--];	for (m=1;m<n;m++) {		for (i=1;i<=n-m;i++) {			ho=xa[i]-x;			hp=xa[i+m]-x;			w=c[i+1]-d[i];			if ( (den=ho-hp) == 0.0) nrerror("Error in routine polint");			den=w/den;			d[i]=hp*den;			c[i]=ho*den;		}		*y += (*dy=(2*ns < (n-m) ? c[ns+1] : d[ns--]));	}	free_vector(d,1,n);	free_vector(c,1,n);}#undef NRANSI