multiplication.cpp

#include<iostream>
using namespace std;
int main()
{


    int a[]={1,2,3,4};
    int b[]={5,6,7,8};
    int i,j=3,c,k,u; //j=array length, k for loop, c for array reversing

    //code for reversing index
    for(i=0;i<=j/2;i++)
    {
        c=a[i];
        a[i]=a[j-i];
        a[j-i]=c;
        c=b[i];
        b[i]=b[j-i];
        b[j-i]=c;
    }

//end of reversing code

    long long int d[2*j+1];
    for(i=0;i<2*j+1;i++)
    {
        d[i]=0;
    }





     for(i=0,u=2*j;i<=j;i++,u--)
    {
        for(k=0;k<=i;k++)
        {
            d[i]+=a[k]*b[i-k];
            if(u!=i)
            {
                d[u]+=a[j-k]*b[j+k-i];
            }

        }

    }




    // code for final approach
    for(i=0;i<2*j+1;i++)
    {
        d[i+1]+=d[i]/10;
        d[i]%=10;

    }



     for(i=0;i<j*2+1;i++)
    cout<<d[i]<<endl;





    return 0;
}