QueueStack.cpp

#include <iostream>
#include <stack>

using namespace std;

class Queue {
private:
    stack<int> e_stk;
    stack<int> d_stk;
public:
    Queue() {};
    ~Queue() {};
    void enqueue(int x);
    int dequeue();
};

void Queue::enqueue(int x) {
    e_stk.push(x);
}

int Queue::dequeue() {
    int x = -1;
    if (d_stk.empty()) {
        if (e_stk.empty()) {
            cout << "Queue Underflow" << endl;
            return x;
        }
        else {
            while (!e_stk.empty()) {
                d_stk.push(e_stk.top());
                e_stk.pop();
            }
        }
    }
    x = d_stk.top();
    d_stk.pop();
    return x;
}

int main() {

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

    Queue q;

    cout << "Enqueue: " << flush;
    for (int i = 0; i < sizeof(A) / sizeof(A[0]); i++) {
        q.enqueue(A[i]);
        cout << A[i] << flush;
        if (i < sizeof(A) / sizeof(A[0]) - 1) {
            cout << " <- " << flush;
        }
    }
    cout << endl;

    cout << "Dequeue: " << flush;
    for (int i = 0; i < sizeof(A) / sizeof(A[0]); i++) {
        cout << q.dequeue() << flush;
        if (i < sizeof(A) / sizeof(A[0]) - 1) {
            cout << " <- " << flush;
        }
    }

    return 0;
}