LinkedList.cpp

#include "LinkedList.h"
#include <iostream>
using namespace std;

//constructor
LinkedList::LinkedList() {
    head = nullptr;
    tail = nullptr;
    length = 0;
}

//destructor
LinkedList::~LinkedList() {
    Node* temp;

    while (head != nullptr) {
        temp = head;
        head = head->next;
        delete temp;
    }

    tail = nullptr;
    length = 0;
}

//prepend element in the linkedlist
void LinkedList::insertAtHead(int data) {
    Node* newNode = new Node;
    newNode->data = data;

    newNode->next = head;
    head = newNode;

    if (tail == nullptr) {
        tail = newNode;
    }

    length++;
}

//append element in the linkedlist
void LinkedList::insertAtEnd(int data) {
    Node* newNode = new Node;
    newNode->data = data;
    newNode->next = nullptr;

    if (head == nullptr) {
        head = newNode;
        tail = newNode;
    }
    else {
        tail->next = newNode;
        tail = newNode;
    }

    length++;
}

//delete a data anywhere in the linkedlist
void LinkedList::deletedata(int data) {
    if (head == nullptr) {
        cout << "List is empty" << endl;
        return;
    }

    if (head->data == data) {//List had only one node
        Node* temp = head;
        head = head->next;

        if (head == nullptr) {
            tail = nullptr;// after deleting the node, tail must also be reset to null
        }

        delete temp;
        length--;
        return;
    }

    Node* current = head;

    while (current->next != nullptr && current->next->data != data) {
        current = current->next;
    }

    if (current->next == nullptr) {
        cout << "data not found" << endl;
        return;
    }

    Node* temp = current->next;
    current->next = temp->next;

    if (temp == tail) {// moving tail back to the previous node as the deleted node was the tail
        tail = current;
    }

    delete temp;
    length--;
}

//display elements in the linkedlist
void LinkedList::display() {
    Node* temp = head;

    while (temp != nullptr) {
        cout << temp->data << " -> ";
        temp = temp->next;
    }

    cout << "NULL" << endl;
}