0001 template <typename T> void List<T>::reverse() { //前后倒置
0002    LNP<T> p = head;  LNP<T> q = tail; //头、尾节点
0003    for (Rank i = 1; i < _size; i += 2) //（从首、末节点开始）由外而内，捉对地
0004       swap((p = p->succ)->data, (q = q->pred)->data); //交换对称节点的数据项
0005 } //reverse()