Binary Queue

#include <iostream>
#include <fstream>

#define MAX 5

class Queue {
private:
    int q[MAX];  // Array to hold queue elements
    int front;   // Index of the front element
    int rear;    // Index of the rear element
    std::string filename; // Name of the binary file

public:
    Queue(std::string fname) : front(-1), rear(-1), filename(fname) {}

    void enqueue(int value);
    void dequeue();
    void display();
    void loadQueue(); // Load queue from file
    void saveQueue(); // Save queue to file
};

void Queue::enqueue(int value) {
    if ((front == 0 && rear == MAX - 1) || (rear + 1 == front)) {
        std::cout << "Queue is full.\n";
        return;
    }
    if (front == -1) { // If queue is empty
        front = 0;
        rear = 0;
    } else {
        rear = (rear + 1) % MAX; // Circular increment
    }
    q[rear] = value;
    saveQueue(); // Save the updated queue to file
    std::cout << value << " enqueued to the queue.\n";
}

void Queue::dequeue() {
    if (front == -1) {
        std::cout << "Queue is empty.\n";
        return;
    }
    std::cout << q[front] << " dequeued from the queue.\n";
    if (front == rear) { // If queue has only one element
        front = rear = -1; // Reset the queue
    } else {
        front = (front + 1) % MAX; // Circular increment
    }
    saveQueue(); // Save the updated queue to file
}

void Queue::display() {
    if (front == -1) {
        std::cout << "Queue is empty.\n";
        return;
    }
    std::cout << "Queue elements: ";
    for (int i = front; i != rear; i = (i + 1) % MAX) {
        std::cout << q[i] << " ";
    }
    std::cout << q[rear] << "\n"; // Display the rear element
}

void Queue::loadQueue() {
    std::ifstream infile(filename, std::ios::binary);
    if (infile.is_open()) {
        infile.read(reinterpret_cast<char*>(&front), sizeof(front));
        infile.read(reinterpret_cast<char*>(&rear), sizeof(rear));
        infile.read(reinterpret_cast<char*>(q), sizeof(q));
        infile.close();
    }
}

void Queue::saveQueue() {
    std::ofstream outfile(filename, std::ios::binary);
    if (outfile.is_open()) {
        outfile.write(reinterpret_cast<char*>(&front), sizeof(front));
        outfile.write(reinterpret_cast<char*>(&rear), sizeof(rear));
        outfile.write(reinterpret_cast<char*>(q), sizeof(q));
        outfile.close();
    }
}

int main() {
    Queue queue("queue_data.bin");
    queue.loadQueue(); // Load the queue from the binary file

    int choice, value;
    do {
        std::cout << "1. Enqueue\n2. Dequeue\n3. Display\n4. Exit\n";
        std::cout << "Enter your choice: ";
        std::cin >> choice;
        switch (choice) {
            case 1:
                std::cout << "Enter value to enqueue: ";
                std::cin >> value;
                queue.enqueue(value);
                break;
            case 2:
                queue.dequeue();
                break;
            case 3:
                queue.display();
                break;
            case 4:
                std::cout << "Exiting...\n";
                break;
            default:
                std::cout << "Invalid choice. Please try again.\n";
        }
    } while (choice != 4);

    return 0;
}