【数据结构】双向带头循环链表的C语言代码实现

ListNode* ListInit()
{
    ListNode*phead = BuyListNode(0);
    phead->next = phead;//
    phead->prev = phead;
    return phead;
}

void ListPushBack(ListNode*phead, LTDataType x)
{
    ListNode*tail = phead->prev;//
    ListNode*newnode = BuyListNode(x);
    tail->next = newnode;
    newnode->prev = tail;
    newnode->next = phead;
    phead->prev = newnode;
}

void ListPrint(ListNode*phead)
{
    ListNode*cur = phead->next;
    while (cur != phead)
    {
        printf("%d   ", cur->data);
        cur = cur->next;
    }
    printf("\n");
}

void ListPopFront(ListNode*phead, LTDataType x)
{
    ListNode*first = phead->next;
    ListNode*newnode = BuyListNode(x);
    phead->next = newnode;
    newnode->prev = phead;
    newnode->next = first;
    first->prev = newnode;
}

void ListPopFront(ListNode*phead, LTDataType x)
{
    
    ListNode*first = phead->next;
    ListNode*second = first->next;
    phead->next = second;
    second->prev = phead;
    free(first);
}

void ListPopBack(ListNode*phead)
{
    assert(phead->next != phead);//判断是不是一个节点也没有
    ListNode*tail = phead->prev;
    ListNode*prev = tail->prev;
    prev->next = phead;
    phead->prev = prev;
    free(tail);
    tail = NULL;
}