Simple Single Linked List Implementation in C++

linkedlist_s.cpp

#include <iostream>
using namespace std;
#define null 0

class Node {
public:
    int data;
    Node *next;
    Node(int data) {
        this->data = data;
        next = NULL;
    }
};

class LinkedList {
private:
    Node *head;
    Node *tail;
    int size;
    
public:
    LinkedList() {
        head = NULL;
        tail = NULL;
        size = 0;
    }
    void append(int data) {
        Node *node = new Node(data);
        if(head == NULL) {
            head = node;
            tail = node;
        } else {
            tail->next = node;
            tail = node;
        }
        size++;
    }
    void prepend(int data) {
        Node *node = new Node(data);
        if(head == NULL) {
            head = node;
            tail = node;
        } else {
            node->next = head;
            head = node;
        }
        size++;
    }
    void insertAt(int data, int pos) {
        if(pos > size+1 || pos < 1) return;
        else if(pos == 1) prepend(data);
        else if(pos == size+1) append(data);
        else if(head != NULL) {
            Node *node = new Node(data);
            Node *prev;
            Node *current = head;
            for(int i = 1; i < pos; i++) {
                prev = current;
                current = current->next;
            }
            prev->next = node;
            node->next = current;
            size++;
        }
    }
    void removeHead() {
        if(head != NULL) {
            Node *current = head;
            head = head->next;
            delete(current);
            size--;
        }
    }
    void removeTail() {
        if(head->next == NULL) removeHead();
        else if(head != NULL) {
            Node *current = head;
            Node *prev;
            while(current->next != NULL) {
                prev = current;
                current = current->next;
            }
            tail = prev;
            prev->next = NULL;
            delete(current);
            size--;
        }
    }
    void removeAt(int pos) {
        if(pos > size || pos < 1) return;
        else if(pos == 1) removeHead();
        else if(pos == size) removeTail();
        else if(head != NULL) {
            Node *prev;
            Node *current = head;
            for(int i = 1; i < pos; i++) {
                prev = current;
                current = current->next;
            }
            prev->next = current->next;
            delete(current);
            size--;
        }
    }
    void remove(int data) {
        if(head != NULL) {
            Node *current = head;
            if(current->data == data) {
                head = head->next;
                delete(current);
            } else {
                while(current != NULL) {
                    if(current->next->data == data) {
                        current->next = current->next->next;
                        break;
                    } else {
                        current = current->next;
                    }
                }
            }
        }
    }
    void print() {
        Node *current = head;
        while(current != NULL) {
            cout << current->data << endl;
            current = current->next;
        }
        cout << endl;
    }
    void test() {
        prepend(3);
        prepend(1);
        prepend(5);
        print();
        append(8);
        append(7);
        print();
        insertAt(2, 9);
        insertAt(4, 11);
        print();
        removeHead();
        print();
        removeAt(3);
        print();
        removeTail();
        print();
    }
    ~LinkedList() {
        Node *current;
        while(head != NULL) {
            current = head->next;
            delete(head);
            head = current;
        }
        head = NULL;
        tail = NULL;
    }
};

int main() {
    LinkedList list;
    list.test();
    return 0;
}