Lagrange interpolation formula in c++

  Solution in C++: 

///******Bismillahir-Rahmanir-Rahim******///

///AH Tonmoy

///Department of CSE,23rd batch

///Islamic University,Bangladesh

#include<bits/stdc++.h>

using namespace std;

int main()

{

     double x[1000], y[1000], xp,findpoint, yp=0,p,fxsum;

     int i,j,n;

     cout<<"Enter number of data: ";

     cin>>n;

     cout<<"Enter data:"<< endl;

     for(i=1;i<=n;i++)

     {

          cout<<"x["<< i<<"] = ";

          cin>>x[i];

          cout<<"y["<< i<<"] = ";

          cin>>y[i];

     }

     cout<<"Enter interpolation point: ";

     cin>>findpoint;

     //  Lagrange Interpolation implement

     for(i=1;i<=n;i++)

     {

          p=1;

          for(j=1;j<=n;j++)

          {

               if(i!=j)

               {

                    p = p* (findpoint - x[j])/(x[i] - x[j]);

               }

          }

          fxsum=fxsum + p * y[i];

     }

     cout<< endl<<"  Interpolated value at  "<< findpoint<< "  is    "<< fxsum;

     return 0;

}