интерполяция по Лагранжу

# include <iostream.h>
# include <conio.h>
# include <fstream.h>
# include <iomanip.h>
 
 int main()
{
   int n;
   double delta=0.1;
//________________________________________________________
   
   ifstream infile ("coordinates.txt");
   ofstream outfile ("points.txt");
   infile>>n;
//________________________________________________________ 
   
   double*X=new double [n];
   double*Y=new double [n];
//_______________________________________________________
   
   for( int i=0; i<n; i++)
   { infile>>X[i]>>Y[i]; }
//_______________________________________________________
   
   double a=X[0], b=X[n-1];
   
   for(double x=a; x<=b; x+=delta)
   {  
      double y=0;
      
      for(int i=0;i<n;i++)
      {
         double P=1;
         
         for(int j=0;j<n;j++)
         { 
            if(i!=j)
               P*=(x-X[j])/(X[i]-X[j]);
         }
         y+=Y[i]*P;
      } 
            outfile<<x<<setw(20)<<y<<endl;
    }
    
    cout<<" Looking for the results of interpolation in file <<points.txt>> . "<<endl;
//_______________________________________________________
 
    delete X; 
    delete Y;
//________________________________________________________
 
  infile.close();
  outfile.close();
//_______________________________________________________
  
  getch ();  
  return 0;
}