Question

I need to understand how a linked list works in this C++ code. I got it from my textbook. Could someone explain in detail what exactly is going on here?

/*The  Node Class*/
class Node{
    private:
        int object;
        Node *nextNode;  

    public:            
        int get()
        {
            return object;    
        }
        void set(int object)
        {
            this-> object=object;     
        }
        Node *getNext()
        {
            return nextNode;     
        };
        void setNext(Node *nextNode)
        {
            this->nextNode = nextNode;
        };
};



/* The List class */
class List
{
    public:
        List();
        void add (int addObject);
        int get();
        bool next();
        friend void traverse(List list);
        friend List addNodes();
    private:
        int size;
        Node * headNode;
        Node * currentNode;
        Node * lastCurrentNode;
};
/* Constructor */
List::List()
{
    headNode = new Node();
    headNode->setNext(NULL);
    currentNode = NULL;
    lastCurrentNode = NULL;
    size = 0;
}
/* add() class method */
void List::add (int addObject)
{
    Node * newNode = new Node();
    newNode->set(addObject);
    if( currentNode != NULL )
    {
        newNode->setNext(currentNode->getNext());
        currentNode->setNext( newNode );
        lastCurrentNode = currentNode;
        currentNode = newNode;
    }
    else
    {
        newNode->setNext(NULL);
        headNode->setNext(newNode);
        lastCurrentNode = headNode;
        currentNode = newNode;
    }
    size ++;
}
/* get() class method */
int List::get()
{
    if (currentNode != NULL)
        return currentNode->get();
}
/* next() class method */
bool List::next()
{
    if (currentNode == NULL) return false;
    lastCurrentNode = currentNode;
    currentNode = currentNode->getNext();
    if (currentNode == NULL || size == 0)
        return false;
    else
        return true;
}
/* Friend function to traverse linked list */
void traverse(List list)
{
    Node* savedCurrentNode = list.currentNode;
    list.currentNode = list.headNode;
    for(int i = 1; list.next(); i++)
    {
        cout<<"\n Element "<<i<<" "<<list.get();
    }
    list.currentNode = savedCurrentNode;
}
/* Friend function to add Nodes into the list */
List addNodes()
{
    List list;
    list.add(2);
    list.add(8);
    list.add(7);
    list.add(1);
    cout<<"\n List size = "<<list.size<<"\n";
    return list;
}


main()
{
    List list = addNodes();
    traverse(list);

    system("pause");
}

Answer 1

what you’ve posted is a very basic implementation of a linked list. The objects that you’re linking is “node”.

GetNext function gets the next node in the list
and the setNex function gets the next node in the list.

i’m sure the chapter should have an explanation for the code, at the very least the explanation for the concept of linked list.

hope this helps.