以单链表表示集合，设计算法建立先后输入的两个集合的差。

说明：已知两个集合A和B，集合A-B中包含所有属于集合A而不属于集合B的元素。

步骤：1.首先建立A和B的单链表

2.然后对集合B中的每个元素x，在A中查找，若存在和x相同的元素，则从该链表中删除。

3.打印A-B，进行验证。

-Expressed as a singly linked list collection, design algorithm has two sets of differential input.

Descr iption: known two sets A and B, set A- B contains all belong to the set and do not belong to the set B elements.

Steps: 1. First of all, establish A and B singly linked lists

2. And then to set each element of x, B in A search, if any, and x of the same element, is deleted　the list.

3. Print A- B, for validation.