Stack and Queue Using Array

#include <iostream>
#include <cstdlib>
#define MAX 10
#define M 10
using namespace std;

class STACK
{
    int top;
    int arr[MAX];

public:
    STACK()
    {
        top = -1;
    }
    bool isempty();
    bool isfull();
    int push(int);
    int pop();
    void display_stack();
};

bool STACK ::isempty()
{
    if (top == -1)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

bool STACK ::isfull()
{
    if (top == MAX - 1)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

int STACK ::push(int n)
{
    if (isfull())
    {
        return 0;
    }
    else
    {
        top++;
        arr[top] = n;
        return arr[top];
    }
}

int STACK ::pop()
{
    if (isempty())
    {
        return 0;
    }
    else
    {
        int temp = arr[top];
        top--;
        return temp;
    }
}

void STACK ::display_stack()
{
    for (int i = top; i >= 0; i--)
    {
        cout << arr[i] << " ";
    }
    cout << endl;
}

class QUEUE
{
    int front, rear;
    int a[M];

public:
    QUEUE()
    {
        front = -1;
        rear = -1;
    }
    bool isfull();
    bool isempty();
    int enqueue(int);
    int dequeue();
    void display_queue();
};

bool QUEUE ::isfull()
{
    if (rear == M - 1)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

bool QUEUE ::isempty()
{
    if (front == -1 && rear == -1 || front > rear)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

int QUEUE ::enqueue(int n)
{
    if (isfull())
    {
        return 0;
    }
    else
    {
        if (isempty())
        {
            front = 0;
            rear++;
            a[rear] = n;
            return a[rear];
        }
        else
        {
            rear++;
            a[rear] = n;
            return a[rear];
        }
    }
}

int QUEUE ::dequeue()
{
    if (isempty())
    {
        return 0;
    }
    else
    {
        int temp = a[front];
        front++;
        return temp;
    }
}
void QUEUE ::display_queue()
{
    for (int i = front; i <= rear; i++)
    {
        cout << a[i] << " ";
    }
    cout << endl;
}
int main()
{
    STACK s;
    QUEUE q;
    int choice, data, element;
    char opt;
    while (1)
    {
        cout << "1.Stack" << endl
             << "2.Queue" << endl
             << "3.Exit" << endl;
        cin >> choice;
        switch (choice)
        {
        case 1:
            do
            {
                cout << "a.Push" << endl
                     << "b.Pop" << endl
                     << "c.Display Stack" << endl
                     << "d.Exit from Stack"<<endl;
                cin >> opt;
                switch (opt)
                {
                case 'a':
                    cout << "Enter the element to add in stack:" << endl;
                    cin >> data;
                    element = s.push(data);
                    if (element == 0)
                    {
                        cout << "Stack is full" << endl;
                    }
                    else
                    {
                        cout << element << " pushed successfully." << endl;
                    }
                    break;
                case 'b':
                    element = s.pop();
                    if (element == 0)
                    {
                        cout << "Stack is empty" << endl;
                    }
                    else
                    {
                        cout << element << " poped successfully." << endl;
                    }
                    break;
                case 'c':
                    s.display_stack();
                    break;
                }
            } while (opt != 'd');
            break;
        case 2:
            do
            {
                cout << "a.Enqueue" << endl
                     << "b.Dequeue" << endl
                     << "c.Display Queue" << endl
                     << "d.Exit from Queue"<<endl;
                cin >> opt;
                switch (opt)
                {
                case 'a':
                    cout << "Enter the element to add in Queue:" << endl;
                    cin >> data;
                    element = q.enqueue(data);
                    if (element == 0)
                    {
                        cout << "Queue is full" << endl;
                    }
                    else
                    {
                        cout << element << " added successfully." << endl;
                    }
                    break;
                case 'b':
                    element = q.dequeue();
                    if (element == 0)
                    {
                        cout << "Queue is empty" << endl;
                    }
                    else
                    {
                        cout << element << " removed from queue successfully." << endl;
                    }
                    break;
                case 'c':
                    q.display_queue();
                    break;
                }
            } while (opt != 'd');
            break;
        }
    }
}