QUEUELL CPP

// PROGRAM TO IMPLEMENT QUEUE USING LINKED LIST
#include <iostream>

using namespace std;

class node{

protected:
    int element;
    node* link;

public:
    //constructor that accepts only element
    node(int element) {
        this->element = element;
        this->link = NULL;
    }

    //constructor that accepts both link and element
    node(int element, node* link){
        this->element = element;
        this->link = link;
    }

    //method to update the element
    void updateData(int element){
        this->element = element;
    }

    //method to update or setup link
    void updateLink(node* link){
        this->link = link;
    }

    //method to get the element from the node
    int getElement(){
        return this->element;
    }

    //method to get the next node
    node* getNextNode(){
        return this->link;
    }
};

class Linkedlist{
protected:
    node* head;
public:

    //constructor for the Linked List class
    Linkedlist(){
        head = NULL;
    }

    //method returns true if the list is empty
    bool isEmpty(){
        return head == NULL;
    }

    //returns head node
    node* getHead(){
        return this->head;
    }

    //method to add a node at starting
    void addToStart(int element){
        node* tempNode = new node(element);
        if(head == NULL){
            head = tempNode;
        }
        else{
            tempNode->updateLink(head);
            head = tempNode;
        }
    }

    // method to add a node at the end
    void addToEnd(int element){
        node* tempNode = new node(element);
        node* p = head;
        if(head == NULL){
            head = tempNode;
            return;
        }
        else{
            while(p->getNextNode()!= NULL){
                p = p->getNextNode();
            }
            p->updateLink(tempNode);
            return;
        }
    }

    //method to display all the elements of the Linked List
    void display(){
        cout<<"\n";
        node* tempNode = head;
        while(tempNode != NULL){
            if(tempNode->getNextNode() != NULL)
                cout<<tempNode->getElement()<<" --> ";
            else
                cout<<tempNode->getElement();

            tempNode = tempNode->getNextNode();
        }
        return;
    }

    //method to delete a element at a given position
    void deletePosition(int position){
        node* tempNode = head;
        node* prevNode = head;
        if(position == 1){
            head = tempNode->getNextNode();
            return;
        }
        else{
            int pos = 1;
            while(pos != position){
                prevNode = tempNode;
                tempNode = tempNode->getNextNode();
                pos += 1;
            }
            prevNode->updateLink(tempNode->getNextNode());
        }
    }

    bool enqueue(int element){
        if(this->isEmpty()){
            this->addToStart(element);
        }else{
            this->addToEnd(element);
        }
    }

    int dequeue(){
        if(this->isEmpty()){
            cout<<"Queue Empty.";
            return -99999;
        }else{
            int temp = this->head->getElement();
            this->deletePosition(1);
            return temp;
        }
    }

};

int main() {
    Linkedlist l1;
    l1.enqueue(1);
    l1.enqueue(2);
    l1.enqueue(3);
    l1.enqueue(4);
    l1.enqueue(5);
    l1.enqueue(6);

    cout<<"The Contents of the Queue are : ";
    l1.display();

    cout<<"\n\nDequeue 3 elements from the Queue";
    l1.dequeue();
    l1.dequeue();
    l1.dequeue();

    cout<<"\n\nThe Contents of the Queue are : ";
    l1.display();

    return 0;
}

/*

The Contents of the Queue are :
1 --> 2 --> 3 --> 4 --> 5 --> 6

Dequeue 3 elements from the Queue

The Contents of the Queue are :
4 --> 5 --> 6


 */