c++ - 双链表 - 不能删除第一个节点

Question

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

class DoublyLinkedList
{
ofstream cout3;
Node *head; 
public:
DoublyLinkedList()
{
    head = NULL;
    cout3.open("task3.out");
}

void insert(int num)
{
    Node *temp = new Node;
    //To insert if there are no elements
    if(head == NULL)
    {
        temp->prev = NULL;
        temp->data = num;
        temp->next = NULL;
        head = temp;
    }
    //To insert if there are elements
    else
    {
        temp->prev = NULL;
        temp->data = num;
        temp->next = head;
        head->prev = temp;
        head = temp;
    }       
    cout3<<"inserted "<<num<<endl;      
}

void dele(int num)
{
    Node *temp = head;
    int found_num = 0;
    while(temp != NULL)
    {
        if(temp->data == num)
        {
            found_num = 1;
            break;
        }   
        else
            temp = temp->next;
    }
    if(found_num == 0)
        cout3<<"cannot delete "<<num<<endl;
    //To delete first element
    else if (temp->prev == NULL)
    {
        head = temp->next;
        (temp->next)->prev == NULL;
        delete temp;            
        cout3<<"deleted "<<num<<endl;
    }
    //To delete last element
    else if (temp->next == NULL)
    {
        (temp->prev)->next = NULL;
        cout3<<"deleted "<<num<<endl;
        delete temp;
    }
    //To delete any other element
    else
    {
        (temp->prev)->next = temp->next;
        (temp->next)->prev = temp->prev;
        cout3<<"deleted "<<num<<endl;
        delete temp;
    }
}

void search(int num)
{
    Node *temp = head;
    int found_num = 0;
    while(temp != NULL)
    {
        if(temp->data == num)
        {
            found_num = 1;
            break;
        }   
        else
            temp = temp->next;
    }
    if(found_num == 0)
        cout3<<"not found "<<num<<endl;
    else
        cout3<<"found "<<num<<endl;
}

void display()
{
    Node *temp = head;
    while(temp != NULL)
    {
        cout3<<temp->data<<" ";
        temp = temp->next;
    }
    cout3<<endl;
}
};

我的双向链表实现。我只在开头插入并删除第一次出现的数字。但是，如果我想删除第一个元素，那么它会打印“已删除 number”，但是当我显示该数字时，它仍然存在。问题似乎出在我的删除功能上，但我找不到它是什么

Answer 1

看到这一行:(temp->next)->prev == NULL;你写了 == 而不是 = ，这似乎是问题所在。您没有显示如何打印该值，但我猜您在开始之前向后移动直到空值..