1.　　编写主函数测试单链表的各种基本运算:

(1)　　生成一个单链表,链表中的元素由计算机输入

(2)　　在表中的第5个位置上插入元素”7”

(3)　　删除表中的第6个元素

(4)　　显示(1)—(4)每一步的操作结果

-1. Write a main function test singly linked lists of all kinds of basic operations:

(1) to generate a singly linked list, list of elements in the input by computer

(2) in the fifth position in the table to insert elements　7　

(3) remove the sixth element in the table

(4) show that (1)- (4) every step of the operation results