有两个按元素值递增有序排列的链表l1和l2，编写一个程序将l1和l2表归并成一个按元素递增有序的链表l3，要求 (1)链表中允许有相同的元素，只要l1、l2、l3单调不减即可 (2)要利用原表空间(即l1和l2表)的结点空间构造l3。-There are two elements of the value increase ordered by the list l1 and l2, write a program that will merge l1 and l2 table into