编写一个程序，采用单链表表示集合（集合中不存在重复的元素），利用例2.4的算法将其按递增方式排序，构成有序单链表。求这样的两个集合的并、交和差。-prepared a procedure, single chain said pool (pool, there is no duplication of elements), 2.4 cases using the algorithm based on the progressive sorting, orderly single-chain form. For the two pools, intersection and the poor.