#include <iostream>
using namespace std;
class Node {
public:
int data;
Node* next;
Node* prev;
};
class DoublyLinkedList {
private:
Node* head;
Node* tail;
public:
DoublyLinkedList() {
head = nullptr;
tail = nullptr;
}
void append(int data) {
Node* newNode = new Node();
newNode->data = data;
newNode->next = nullptr;
if (head == nullptr) {
newNode->prev = nullptr;
head = newNode;
tail = newNode;
} else {
newNode->prev = tail;
tail->next = newNode;
tail = newNode;
}
}
void display() {
Node* current = head;
while (current != nullptr) {
cout << current->data << " ";
current = current->next;
}
cout << endl;
}
};