Queue_using_2-Stacks.cpp

#include <bits/stdc++.h>
using namespace std;

class Queue
{
private:
    stack<int> stack1;
    stack<int> stack2;

public:
    void enqueue(int data)
    {
        stack1.push(data);
    }

    void dequeue()
    {
        int data;

        if (stack1.empty() && stack2.empty()) //if both stack-1 and stack-2 are empty
        {
            cout << endl
                 << "Queue is empty." << endl;
            return;
        }

        else if (stack2.empty()) //if stack-2 is empty then insert elements from stack-1 to stack-2
        {
            while (!stack1.empty())
            {
                data = stack1.top();
                stack1.pop();
                stack2.push(data);
            }
        }

        data = stack2.top();
        stack2.pop();

        cout << endl
             << data << " is deleted." << endl;
    }

    void display()
    {
        stack<int> stack11;
        stack<int> stack22;
        stack11 = stack1;
        stack22 = stack2;

        while (!stack22.empty())
        {
            cout << endl
                 << "Data = " << stack22.top();
            stack22.pop();
        }

        while (!stack11.empty())
        {
            cout << endl
                 << "Data = " << stack11.top();
            stack11.pop();
        }
    }
};

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

    while (1)
    {
        cout << endl;
        cout << "1. To Enter data into queue." << endl;
        cout << "2. To Delete data from queue." << endl;
        cout << "3. To Display the data." << endl;
        cout << "4. TO EXIT." << endl;

        cout << "\nENTER YOUR CHOICE... : ";
        cin >> choice;

        switch (choice)
        {
        case 1:
            cout << endl
                 << "Enter data to be inserted : ";
            cin >> data;
            q.enqueue(data);
            break;

        case 2:
            q.dequeue();
            break;

        case 3:
            q.display();
            break;

        case 4:
            exit(0);
            break;

        default:
            cout << "\nINVALID CHOICE..." << endl;
        }
    }
    return 0;
}