动态链表插入排序如何插入了表尾

//作业的排序

SeQueue& SeQueue::order()
{
    JCB *t, *p, *pre, *old;

    old = front->next;  //将原链表头结点的下一个结点作为新结点
    front->next = NULL; //截断旧头结点作为新链表头结点
    
    while (old != NULL)     //原表不为空时进行排序
    {
        t = old;            //取原表头结点
        old = old->next;     //指向原表下一个结点
        p = front;         //新表移动指针
        pre = front;       //保存移动时的前驱

        while (t->length >= p->length && p != NULL) //进行比较
        {
            pre = p;
            p = p->next;
        }

        if (p == NULL)    //插入到表尾     
        {
            pre->next = t;
            t->next = NULL;            
        }
        else
        {
            if (p == pre)        //插入到表头
            {
                t->next = p;
                front = t;
            }
            else                //插入到表中间
            {
                pre->next = t;
                t->next = p;
            }
        }

    return *this;
}

请大家分析一下当插入到表尾时有什么问题