设有n个待排序元素存放在单链表中，每个链表结点只存放一个元素，头指针为r，试设计算法对其进行二路归并排序，要求不移动结点中的元素，只修改各链结点中的指针，排序后r仍指向结果链表的第一个结点。-With n-elements to be stored in a single list sorted, each linked list node store only one element, the first pointer to r, test their design algorithm for merge sort, asked not to move the node elements, only the changes The link points to a pointer, r is still pointing to the results sorted list the first node.