如果改用"-2"作为删除标记，则可以正确找到707所在的结点。

Question

这个改用"-2"作为删除标记，则可以正确找到707所在的结点。感觉还是找不到707所在的结点吧

Answer 1

以下答案引用自GPT-3大模型,请合理使用：

不可以，改用“-2”作为删除标记的情况下，并不能正确找到707节点所在的位置。原因是，当使用-2作为删除标记时，遍历循环也会遍历到“-2”这个节点，这时候得到的结果就和之前不一样了。如果要正确找到707所在的结点，应该使用删除指针来完成，代码如下：

struct node
{
    int data;
    struct node *next;
    struct node *prev;
} 
 
int find_element(struct node *head, int element)
{
    struct node *curr = head;
 
    while (curr != NULL) 
    {
        if (curr->data == element) 
            return 1;
        curr = curr->next;
    }
 
    return 0; 
}
 
void deleteNode(struct node** head, int position)
{
    //首先声明一个struct node类型指针，指向head结点
    struct node* current/*移动指针*/, *prev/*记录前驱结点*/;
    int i;
    current = *head;
 
    if (position == 0)//如果删除头结点
    {
        *head = (*head)->next;
    }
    else
    {
        for (i = 0; current != NULL && i < position ; i++)
        {
            prev = current;
            current = current->next;
        }
 
        //如果position大于链表长度
        if (current == NULL) 
            return;
 
        prev->next = current->next;
    }
    free(current);
}
 
int main()
{
    struct node *head = NULL;
    struct node *second = NULL;
    struct node *third = NULL;
 
    // 动态内存分配 
    head  = (struct node *)malloc(sizeof(struct node));  
    second = (struct node *)malloc(sizeof(struct node)); 
    third  = (struct node *)malloc(sizeof(struct node)); 
 
    head->data   = 777;       
    head->next   = second;    
    head->prev   = NULL;    
 
    second->data  = 607;      
    second->next  = third; 
    second->prev  = head;     
 
    third->data   = 707;        
    third->next   = NULL;   
    third->prev   = second; 
 
    if(find_element(head, 707)) 
    {
        printf("Element found."); 
    }
    else
    {
        printf("Element not found.");
    }
 
    deleteNode(&head, 2);
 
    return 0;
}

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