11. Node copy constructor

• Since Node implementation is using pointers, a copy constructor is absolutely crucial to programmer's peace of mind!

  
  class Node {
      friend void print_list( Node const& head );
      Node* pnext;
  public:
      int data;
  
      // Constructor taking initial value:
      Node( int value = 0 )
      : pnext( NULL ), data( value )
      {
      }
  
      // Copy constructor:
      Node( Node const& other )
          : pnext( NULL ), data( other.data )
      {
      }
  };