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。-Let A and B are two nodes with the first order circular list (the so-called point of order is the link to the link at the size of data field values, this question may wish to set the threshold according to data from small to large order), list1 and list2 are head of the list to point to the two pointer. Please write the two lists into one ordered to take the lead node algorithm for circular linked list.