循环双链表的拆分 满足用递归的形式实现链表的销毁，只出现一次free，用户可自行选择前插或后插法

以下是使用递归实现循环双链表拆分并销毁的代码，其中用户可以选择前插或后插法：

#include <stdio.h>
#include <stdlib.h>

typedef struct node {
    int data;
    struct node* prev;
    struct node* next;
} Node;

Node* createNode(int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

void insertNode(Node** head, int data, int insertType) {
    Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
        (*head)->prev = *head;
        (*head)->next = *head;
        return;
    }
    if (insertType == 0) { // 前插法
        newNode->prev = (*head)->prev;
        newNode->next = *head;
        (*head)->prev->next = newNode;
        (*head)->prev = newNode;
        *head = newNode;
    } else { // 后插法
        newNode->prev = (*head)->prev;
        newNode->next = (*head)->prev->next;
        (*head)->prev->next = newNode;
        (*head)->prev = newNode;
    }
}

void splitList(Node* head, Node** list1, Node** list2, int splitValue) {
    if (head == NULL) {
        return;
    }
    if (head->data <= splitValue) {
        insertNode(list1, head->data, 1); // 后插法插入到list1
    } else {
        insertNode(list2, head->data, 0); // 前插法插入到list2
    }
    splitList(head->next, list1, list2, splitValue);
    free(head);
}

void printList(Node* head) {
    if (head == NULL) {
        printf("NULL\n");
        return;
    }
    Node* current = head;
    do {
        printf("%d <-> ", current->data);
        current = current->next;
    } while (current != head);
    printf("Head\n");
}

int main() {
    Node* head = NULL;
    insertNode(&head, 8, 0);
    insertNode(&head, 6, 0);
    insertNode(&head, 7, 0);
    insertNode(&head, 5, 0);
    insertNode(&head, 4, 0);
    insertNode(&head, 3, 0);
    insertNode(&head, 2, 0);
    insertNode(&head, 1, 0);
    printf("Original list:\n");
    printList(head);
    Node* list1 = NULL;
    Node* list2 = NULL;
    splitList(head, &list1, &list2, 5);
    printf("List1:\n");
    printList(list1);
    printf("List2:\n");
    printList(list2);
    return 0;
}

在上面的代码中，`insertNode`函数用于在循环双链表中插入新节点。`splitList`函数用于实现循环双链表的拆分，并将较小或等于拆分值的节点插入到`list1`中，将较大的节点插入到`list2`中。`printList`函数用于打印循环双链表。在主函数中，我们先创建一个循环双链表，然后调用`splitList`函数进行拆分。最后打印拆分后的两个链表。