5linearqueue_array.cpp

// 5. Implement Linear Queue ADT using array.

// Theory:
// This code implements a queue data structure using an array. It 
// provides functionalities to enqueue elements into the queue, 
// dequeue elements from the queue, and display the elements currently 
// in the queue. The main function offers a menu-driven interface for 
// users to interact with the queue.

#include <iostream>
using namespace std;

const int MAX_SIZE = 100;

class Queue 
{
private:
    int front, rear;
    int arr[MAX_SIZE];

public:
    Queue() 
    {
        front = -1;
        rear = -1;
    }

    bool isEmpty() 
    {
        return (front == -1 && rear == -1);
    }

    bool isFull() 
    {
        return (rear == MAX_SIZE - 1);
    }

    void enqueue(int data) 
    {
        if (isFull()) 
        {
            cout << "queue is full" << endl;
            return;
        } 
        else if (isEmpty()) 
        {
            front = rear = 0;
        } 
        else 
        {
            rear++;
        }
        
        arr[rear] = data;
        cout << data << " enqueued to queue" << endl;
    }

    void dequeue() 
    {
        if (isEmpty()) 
        {
            cout << "queue is empty" << endl;
            return;
        } 
        else if (front == rear) 
        {
            cout << arr[front] << " dequeued from queue" << endl;
            front = rear = -1;
        } 
        else 
        {
            cout << arr[front] << " dequeued from queue." << endl;
            front++;
        }
    }

    void display() 
    {
        if (isEmpty()) 
        {
            cout << "queue is empty" << endl;
            return;
        }
        
        cout << "elements in the queue: ";

        for (int i = front; i <= rear; i++) 
        {
            cout << arr[i] << " ";
        }
        cout << endl;
    }
};

int main() 
{
    Queue q;
    int choice, data;

    do {
        cout << "\n1. enqueue\n";
        cout << "2. dequeue\n";
        cout << "3. display\n";
        cout << "4. exit\n";
        cout << "choose an option : ";
        cin >> choice;

        switch(choice) 
        {
            case 1:
                cout << "enter elements to enqueue: ";
                cin >> data;
                q.enqueue(data);
                break;
            case 2:
                q.dequeue();
                break;
            case 3:
                q.display();
                break;
            case 4:
                cout << "exited!" << endl;
                break;
            default:
                cout << "invalid choice." << endl;
        }
    } 
    while (choice != 4);

    return 0;
}

// Conclusion:
// The code offers a basic implementation of a queue using an array, 
// providing essential operations such as enqueue, dequeue, and 
// display. It offers a user-friendly menu interface for interacting 
// with the queue, allowing users to enqueue elements, dequeue 
// elements, and view the elements currently in the queue.