说明：  1.单链表反转 2.找出单链表的倒数第4个元素 3.找出单链表的中间元素 4.删除无头单链表的一个节点 5.两个不交叉的有序链表的合并 6.有个二级单链表，其中每个元素都含有一个指向一个单链表的指针。写程序把这个二级链表称一级单链表。 7.单链表交换任意两个元素（不包括表头） 8.判断单链表是否有环？如何找到环的“起始”点？如何知道环的长度？ 9.判断两个单链表是否相交 10.两个单链表相交，计算相交点 11.用链表模拟大整数加法运算 12.单链表排序 13.删除单链表中重复的元素
(1 single list reversal 2. Identify a single list of the penultimate four elements 3. Identify a single list of middle element 4. Delete a single list of a headless node 5. Two non-intersecting ordered list merger of six There is a two single linked list, where each element contains a pointer pointing to a single list. Put the two lists write a program known as a single list. 7 single list swap any two elements (not including the header) 8. Determine whether there is a single chain ring? How to find the ring " start" point? How do we know the length of the ring? 9 determine whether the intersection of two single chain 10 intersected two single linked list, calculate the intersection point 11. Using chain simulation large integer adder 12. Single list sorting 13. Delete duplicate elements in a single list)