0001 template <typename T> void List<T>::reverse() { //前后倒置
0002    if (_size < 2) return; //平凡情况
0003    for (LNP<T> p = head; p; p = p->pred) //自前向后，依次
0004       swap(p->pred, p->succ); //交换各节点的前驱、后继指针
0005    swap(head, tail); //头、尾节点互换
0006 } //reverse()