鏈表反轉

void reverse(Node*& head)
{
    if (!head)
        return;
    Node *p1, *p2, *p3;
    p1 = head;
    p2 = p1->next;
    p1->next = NULL;
    while (p2)
    {
        p3 = p2->next;
        p2->next = p1;
        p1 = p2;
        p2 = p3;
    }
    head = p1;
}