Question

I’m trying to overload the += operator in my program. It consists of a polynomial class that includes an int degree (the highest degree of the polynomial) and a Node* Poly (a pointer to a node)

struct Node{ int coefficient;
             Node* next; };

that is my Node struct, I am overloading in the Polynomial class though.

  Polynomial& Polynomial::operator +=(const Polynomial& rP){
    Polynomial copyRP(rP);
    poly->coefficient = poly->coefficient + copyRP.poly->coefficient;
    poly = poly->next; //if I take this and
    copyRP.poly = copyRP.poly->next; //this away, it runs fine
    //with it however the program compiles but doesnt work 
    return *this;
  }

The node contains the list of the coefficients backwards, if that matters. For example 3x^2+2x+5 is stored in the node as 5->2->3 and has a degree of 2.

Answer 1

Try this:

struct polynomial {
    std::vector< int > coeffs;
    std::size_t degree() const { return coeffs.size(); }
};

polynomial &polynomial::operator+= ( polynomial &lhs, polynomial const &rhs ) {
    if ( lhs.degree() < rhs.degree() ) lhs.coeffs.resize( rhs.degree() );
    for ( std::size_t k = 0; k != rhs.degree(); ++ k ) {
        lhs.coeffs[ k ] += rhs.coeffs[ k ];
    }
    return lhs;
}

No linked lists, no manual memory management, you can easily change it to another numeric type.