用C语言合并双向链表

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

Node* list1 = NULL;
Node* list2 = NULL;

// 初始化链表1
// ...

// 初始化链表2
// ...

Node* mergeLists(Node* list1, Node* list2) {
    // 创建一个新的链表头节点
    Node* mergedList = NULL;
    Node* current = NULL;

    // 处理空链表的情况
    if (list1 == NULL) {
        return list2;
    }
    if (list2 == NULL) {
        return list1;
    }

    // 选择较小的节点作为新链表的头节点
    if (list1->data <= list2->data) {
        mergedList = list1;
        list1 = list1->next;
    } else {
        mergedList = list2;
        list2 = list2->next;
    }

    current = mergedList;

    // 遍历两个链表，比较节点的值，将较小的节点连接到新链表中
    while (list1 != NULL && list2 != NULL) {
        if (list1->data <= list2->data) {
            current->next = list1;
            list1->prev = current;
            list1 = list1->next;
        } else {
            current->next = list2;
            list2->prev = current;
            list2 = list2->next;
        }
        current = current->next;
    }

    // 将剩余的节点连接到新链表的末尾
    if (list1 != NULL) {
        current->next = list1;
        list1->prev = current;
    } else {
        current->next = list2;
        list2->prev = current;
    }

    return mergedList;
}