构造一个空链表，销毁链表，将链表置为空表，判断链表是否为空，是返回1，否则返回0，返回链表中元素的个数等功能-Constructs an empty linked list, destroyed linked list, will list the empty table, judge whether the list is empty, is 1, otherwise returns 0 return, return to list the number of elements, and other functions