Implementation Queue Data Structure to visualize JOB Queue by an Operating System using C++

 Problem Statement: Queues are frequently used in computer programming, and a typical example is the creation a job queue by an operating system. If the operating system does not use priorities, then jobs are processed in the order they enter the system. Write C++ program for simulating job queue. Write functions to add delete job from queue.

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#include<iostream>

using namespace std;

class node{

    public:

    int data;

    node* next;

    node(int x){

        data = x;

        next = NULL;

    }

};

class queue{

    public:

    node* front;

    node* rear;

    queue(){

        front = NULL;

        rear = NULL;

    }

    void enqueue(){

        int x;

        cout<<"Enter JOB to be inserted in the Queue : A";

        cin>>x;

        node* n = new node(x);

        if(front==NULL){

            rear = n;

            front = n;

            return;

        }

        rear->next = n;

        rear = n;

    }

   

    void dequeue(){

        if(front==NULL){

            cout<<"Queue is Empty!";

            return;

        }

        node* todelete = front;

        front = front->next;

        delete todelete;

    }

    int frontElement(){

        if(front==NULL){

            cout<<"Queue is Empty!";

            return -1;

        }

        return front->data;

    }

    int rearElement(){

        if(front==NULL){

            cout<<"Queue is Empty!";

            return -1;

        }

        return rear->data;

    }

    int size(){

        if(front==NULL){

            cout<<"Queue is Empty!";

            return 0;

        }

        int sum = 0;

        node* temp = front;

        while(temp!=NULL){

            sum+=1;

            temp = temp->next;

        }

        return sum;

    }

    void displayQueue(){

        if(front==NULL){

            cout<<"Queue is Empty!";

            return;

        }

        node* temp = front;

        while(temp!=NULL){

            cout<<"A"<<temp->data<<" ";

            temp = temp->next;

        }

        cout<<endl;

    }

};

int main(){

    queue q;

    cout<<"Queue Representation:"<<endl;

    char cont = 'y';

    while(cont=='y'){

        int option;

        cout<<"<-----Menu----->"<<endl;

        cout<<"1.Enter JOB in Queue"<<endl;

        cout<<"2.Delete JOB from Queue"<<endl;

        cout<<"3.Display First JOB of Queue"<<endl;

        cout<<"4.Display Last JOB of Queue"<<endl;

        cout<<"5.size of JOB Queue"<<endl;

        cout<<"6.Display JOB Queue"<<endl;

        cout<<"Enter a choice: ";

        cin>>option;

        switch(option){

            case 1: q.enqueue(); break;

            case 2: q.dequeue(); break;

            case 3: cout<<"The First JOB of Queue is: A"<<q.frontElement()<<endl; break;

            case 4: cout<<"The Last JOB of Queue is: A"<<q.rearElement()<<endl; break;

            case 5: cout<<"The size of Queue is: "<<q.size()<<endl; break;

            case 6: cout<<"The JOB queue is: ";q.displayQueue();cout<<endl; break;

            default: cout<<"INVALID Choice!!!"<<endl;

        }

        cout<<"Do you want to continue?(y/n): ";

        cin>>cont;

    }

    if(cont='n'){cout<<"Program Ended succesfully!"<<endl;}

    return 0;

}