说明：  1. 用单向链表实现简单选择排序方法。假设链表中存储的是整数。 2. 用单向链表实现冒泡排序方法。假设链表中存储的是整数。
(1. Using one-way linked list to realize simple selection and sorting method. Suppose that the linked list stores integers. 2. The bubble sorting method is realized by using one-way linked list. Suppose that the linked list stores integers.)