双向链表

如何解决双向链表

我在我的 PopAtEnd 中遇到了分段错误，有人可以帮我吗

#include<iostream>
using namespace std;

class Node{
    public:
    int data;
    Node* next;
    Node* prev;
};

Node* head = NULL;
Node* last = NULL;


void InsertAtBeg(int ele){
    Node* ptr = new Node();
    ptr->data = ele;
    if(head == NULL && last == NULL){
        head = last = ptr;
        ptr->next = NULL;
        ptr->prev = NULL;
        return;
    }
    ptr->prev = NULL;
    ptr->next = head;
    head = ptr;
}

void InsertAtEnd(int ele){
    Node* ptr = new Node();
    ptr->data = ele;
    last->next = ptr;
    ptr->next = NULL;
    last = ptr;

}

void PopAtBeg(){
    Node* temp = head;
    head = head->next;
    head->prev = NULL;
    delete temp;
}

//**Segmentation Fault**//

void PopAtEnd(){
    Node* temp = last;
    last = last->prev;
    last->next = NULL;
    delete temp;
    
}

void display(){
    Node* temp = head;
    int i = 0;
        while(temp->next != NULL){
            cout << temp->data <<" ";
            temp = temp->next;
            i++;
        }
    cout<<temp->data<<endl;
    cout<<"Size of the list is "<<i + 1<<endl;
}

void search(int key){
    Node* temp = head;
    int  i = 0;
    while(temp->next != NULL){
            if(temp->data == key)
                cout<<key<<" is found at index "<<i<<endl;
            temp = temp->next;
            i++;
        }

}

int main()
{
    InsertAtBeg(7);
    InsertAtBeg(2);
    InsertAtBeg(9);
    InsertAtEnd(1);
    InsertAtEnd(3);
    cout<<"The linked list is : ";
    display();
    search(9);
    search(1);
    PopAtBeg();
    PopAtEnd();
    cout<<"The linked list is : ";
    display();

}

提前感谢您的帮助。

解决方法

正如 user4581301 所说，你必须在任何地方设置 prev，不要留空。例如，导致 PopAtEnd() 中的分段错误的原因是您说 last = last->prev; 和 last->prev 为 NULL。因此，您必须在 ptr->prev = last;

之前在 InsertAtEnd() 中添加此行：last = ptr;