04 C++ Circular Queue.cpp

#include <iostream>

using namespace std;

class CircularQueue {
private:
    int size;
    int front;
    int rear;
    int* Q;
public:
    CircularQueue(int size);
    ~CircularQueue();
    bool isFull();
    bool isEmpty();
    void enqueue(int x);
    int dequeue();
    void display();
};

CircularQueue::CircularQueue(int size) {
    this->size = size;
    front = 0;
    rear = 0;
    Q = new int[size];
}

CircularQueue::~CircularQueue() {
    delete[] Q;
}

bool CircularQueue::isEmpty() {
    if (front == rear) {
        return true;
    }
    return false;
}

bool CircularQueue::isFull() {
    if ((rear + 1) % size == front) {
        return true;
    }
    return false;
}

void CircularQueue::enqueue(int x) {
    if (isFull()) {
        cout << "Queue Overflow" << endl;
    }
    else {
        rear = (rear + 1) % size;
        Q[rear] = x;
    }
}

int CircularQueue::dequeue() {
    int x = -1;
    if (isEmpty()) {
        cout << "Queue Underflow" << endl;
    }
    else {
        front = (front + 1) % size;
        x = Q[front];
    }
    return x;
}

void CircularQueue::display() {
    int i = front + 1;
    do {
        cout << Q[i] << flush;
        if (i < rear) {
            cout << " <- " << flush;
        }
        i = (i + 1) % size;
    } while (i != (rear + 1) % size);
}


int main() {

    int A[] = { 1, 3, 5, 7, 9 };

    CircularQueue cq(sizeof(A) / sizeof(A[0]) + 1);

    // Enqueue
    for (int i = 0; i < sizeof(A) / sizeof(A[0]); i++) {
        cq.enqueue(A[i]);
    }

    // Display
    cq.display();
    cout << endl;

    // Overflow
    cq.enqueue(10);

    // Dequeue
    for (int i = 0; i < sizeof(A) / sizeof(A[0]); i++) {
        cq.dequeue();
    }

    // Underflow
    cq.dequeue();

    return 0;
}