说明：  设A与B分别为两个带有头结点的有序循环链表（所谓有序是指链接点按数据域值大小链接，本题不妨设按数据域值从小到大排列），list1和list2分别为指向两个链表的头指针。请写出将这两个链表合并为一个带头结点的有序循环链表的算法
(Set A and B respectively with the first two nodes in an orderly cycle of chain (the so-called orderly means click the link data field value of the size of the link, the title may be established by the data field values from small to large order), list1 and List2 respectively, point to the two pointer list head. Please write the two merged into a single list to take the lead in node list in an orderly cycle of the algorithm)