Adding an element in Linked List

Hello to all..

I'm having a little problem with my program about linked list...when adding an element at the end of the list for a second time, a window that says that the visual c++ 6.0 had an error and needs to be close..i already thought lots of other ways to solve the problem but it just keeps happening again and again..

i'll be posting the code here:

Code:

---



void FunctionAddData(int newData)
{

                node *currentPointer = NULL;
                node *last = NULL;

                currentPointer = root;

                node *tempNode = new node;

                cout<<"Enter a number: ";
                cin>>tempNode -> data;

                tempNode -> next = NULL;
               
                if(tempNode == NULL)
                        return;
                else
                {
                        tempNode -> next = NULL;

                        if(root == NULL)
                        {

                                root = tempNode;
                                last = tempNode;
                        }
                        else
                        {
                                last -> next = tempNode;
                                last = tempNode;
                        }
                }

        main();

        return;
}

---

It's generally helpful to tell us what the error is and what line it occurred on.

I see you're calling main directly which is something you should never do. I'm not ever sure why you'd want to in a function that adds a node to a list.

Quote:

---

Originally Posted by gamer1127

Code:

---


                node *last = NULL;
                // ...
                if(root == NULL)
                {
                        root = tempNode;
                        last = tempNode;
                }
                else
                {
                        last -> next = tempNode;
                        last = tempNode;
                }

---

---

As last is NULL (you are never setting it to anything else), accessing last->next will crash your program.

Code:

---

void FunctionAddData(int newData) // 'newData' is not used.
{

        node *currentPointer = NULL;
        node *last = NULL;

        currentPointer = root;

        node *tempNode = new node;

        cout<<"Enter a number: ";
        cin>>tempNode -> data;

        tempNode -> next = NULL;
       
        if(tempNode == NULL) // If this was true then the previous two lines would have been 'undefined behaviour' (or crash)
            return;
        else
        {
            tempNode -> next = NULL; // You did that a few lines ago!

            if(root == NULL)
            {

                root = tempNode; // I assume 'root' is some global
                last = tempNode; // This is pointless as 'last' has only function scope and will 'disappear' on return.
            }
            else
            {
                last -> next = tempNode; // 'last' has no value set here.
                last = tempNode;
            }
        }

    main(); // 'main' should not be called.

    return;
}

---

What you should be doing is looping through the 'next' pointers starting at 'root' trying to find the last in the list and then adding your new node to this.

Assuming C++, if this function were part of a link list class then the 'root' and 'last' nodes could be stored as private member variables.