bubblesort on a singly linked list

[magic9baller]

I have to use bubblesort to sort a singly linked list. (Yes I am a n00b.) The tricky part is that I have to move pointers rather than moving the contents of one node to the other. I think my problem is incrementing the pointers after a swap. When I didn’t have the code below “THIS IS WRONG,” the function infinitely copied one node into the next. Now that I added that code, I get a segmentation fault. Please help!!

void bubbleSort()
{
..int numCompares = size()-1;
..while (numCompares != 0)
..{
....Node *p = head;
....Node *q = head->next;
....Node *r = head->next->next;
....for (int i = 0; i < numCompares; i++)
....{
......if (r->next->next != NULL && q->val < r->val)
......{
........p->next = r;
........q->next = r->next;
........r->next = q;
........//THIS IS WRONG
........p = p->next;
........q = p->next;
........r = q->next;
......}
......else
......{
........//increment pointers
........r = r->next;
........q = q->next;
........p = p->next;
......}
....}
..}
}