Swapping adjacent elements of linked list

Question

The below is my code to recursive swap the adjacent elements of a linked list. I am losing the pointer to every second element after the swap. The input is 1->2->3->4->5->6-

Answer 1

With no recursion:

void swap(node **head)
{
    while (*head && (*head)->next)
    {
        node* tmp = *head;
        *head = tmp->next;
        tmp->next = (*head)->next;
        (*head)->next = tmp;
        head = &tmp->next;
    }
}

Invoke swap( & list_head_ptr).

---

Alternatively, you can pass the head pointer by reference-to-pointer and utilize a local pointer-to-pointer member:

void swap(node*& head)
{
    node **pp = &head;
    while (*pp && (*pp)->next)
    {
        node* tmp = *pp;
        *pp = tmp->next;
        tmp->next = (*pp)->next;
        (*pp)->next = tmp;
        pp = &tmp->next;
    }
}

and invoke as swap(list_head_ptr). Either method works.