Question

Feel free to edit the title, engrish can sometimes confuse instead of help.

I have to make (and no I can’t change, this is the way it has to be) simple linked list. NO I can’t use STL or std::list. Most of it is done, on paper, but I seem to have a problem implementing a very basic cursor.

This is my Node within the list (part of it):

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

I want to go trough the list in my add node function:

void add_node (Node **begin, int ap_nr)
{
     stuff happens
}

This is how I call the function:

add_node(&(*begin), ap_nr);

I want to create a cursor that starts from begin (the head of my list) and goes trough every node using cursor->next until I reach the end (while (cursor->next!=0))

but I can’t simply say:

Node *cursor;
cursor = new Node;
cursor = begin;

Because this will simply overwrite cursor with begin, making my attempt invalid. I still have to make a pointer to begin and be able to call the STRUCT function “-> next”

How can I do this ?

* ALSO * How can I remember the previous Node ? can I do this:

Node *previous;
previous = new Node;
previous = &(*begin); // ?

Answer 1

It sounds like you want to traverse the list in the add_node function. If so then try the following

void add_node (Node **ppBegin, int ap_nr)
{
  if (!ppBegin) {
    // Need to handle the case of bad user data here
  }

  // Traverse until we get the to the empty next value
  while ((*ppBegin)->next) {
    ppBegin = &((*ppBegin)->next);
  }

  // ppBegin now points to the address of where the new node should go
  Node* created = new Node();
  created->ap_nr = ap_nr;
  *ppBegin = created;
}

Note: To call this function initially you should just call it with add_node(&theListPointer).