Linked List with C++

double_linked_list.cpp

// Online C++ compiler to run C++ program online
#include <iostream>

using namespace std;

struct Node {
    int data;
    
    Node* next;
    Node* prev;
    
    Node(int value): data(value), next(nullptr), prev(nullptr) {}
};

class DoubleLinkedList {
    public: 
    Node* head;
    Node* tail;
    
    DoubleLinkedList(): head(nullptr), tail(nullptr) {}
    
    void insert(int value) {
        Node* newNode = new Node(value);
        
        if(!head) {
            head = tail = newNode;
            return;
        }
        tail->next = newNode;
        newNode->prev = tail;
        
        tail = newNode;
    }
    
    // Display from head to tail
    void displayForward() {
        Node* tmp = head;
        while(tmp) {
            cout << tmp->data << " <-> ";
            tmp = tmp->next;
        }
        cout << "NULL" << endl;
    }
    
    void displayBackward() {
        Node* tmp = tail;
        while(tmp) {
            cout << tmp->data << " -> ";
            tmp = tmp->prev;
        }
        cout << "NULL" << endl;
    }
};

int main() {
    
    DoubleLinkedList list;
    
    list.insert(10);
    list.insert(20);
    list.insert(30);
    list.insert(40);
    list.insert(50);
    
    cout << "Forward traversal: ";
    list.displayForward();
    
    cout << "Backward traversal: ";
    list.displayBackward();

    return 0;
}

single_linked_list.cpp

#include <iostream>

using namespace std;

struct Node {
    int data;
    
    Node* next;
    
    Node(int value): data(value), next(nullptr) {}
};

class SingleLinkedList {
    public: Node* head;
    
    SingleLinkedList(): head(nullptr) {}
    
    void insert(int value) {
        Node* newNode = new Node(value);
        
        if(!head) {
            head = newNode;
            return;
        }
        Node* tmp = head;
        while(tmp->next) {
            tmp = tmp->next;
        }
        
        tmp->next = newNode;
    }
    
    void display() {
        Node* tmp = head;
        while(tmp) {
            cout << tmp->data << " -> ";
            tmp = tmp->next;
        }
        cout << "NULL" << endl;
    }
};

int main() {
    
    SingleLinkedList list;
    
    list.insert(10);
    list.insert(20);
    list.insert(30);
    list.insert(40);
    list.display();

    return 0;
}