Pop in Linked List

Extract the data from the head node, delete the node, advance the head pointer to point at the next node in line. Uses a reference parameter since it changes the head pointer.

int Pop(struct node** headRef) 
{
    struct node* head;
    int result;
    head = *headRef;
    
    assert(head != NULL);
    
    result = head->data; // pull out the data before the node is deleted
    *headRef = head->next; // unlink the head node for the caller
    
    // Note the * -- uses a reference-pointer
    //  just like Push() and DeleteList().
    
    free(head); // free the head node
    return(result); // don't forget to return the data from the link
}