c - 删除链表尾部 : Why a specific approach won't work

Question

我试图理解为什么某个函数会删除链表的尾部而不是另一个。

这是我的链表结构:

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

我的尾插入实现:

node *tail_insert(node *head, int data)
{
    node *temp;

    if (head == NULL)
        return create_doubly_node(data);

    for (temp = head; temp->next != NULL; temp = temp->next)
        ;

    temp->next = create_doubly_node(data);
    temp->next->prev = temp->next;

    return head;

}

这个函数删除尾部:

node *tail_delete(node *head)
{
    node *temp, *prev;

    if (head == NULL)
        return head;

    temp = head;

    while (temp->next != NULL)
    {
        prev = temp;
        temp = temp->next;
    }

    free(temp);
    prev->next = NULL;

    return head;
}

相对于这个:

node *tail_delete(node *head)
{
    node *temp, *prev;

    if (head == NULL)
        return head;

    temp = head;

    while (temp->next != NULL)
    {
        temp = temp->next;
    }

    prev = temp->prev;
    free(temp);
    prev->next = NULL;

    return head;
}

区别在于我如何分配节点 *prev。

Answer 1

您的以下语句是错误的，因为您的 prev 指针指向错误的节点，您的第二种方法不起作用:-

temp->next->prev = temp->next; //here prev is pointing to itself
                               //actually prev = create_doubly_node(data);

更正为:-

 temp->next->prev = temp; //as temp is pointing to the previous node of last node