Class Queue

GeeksForGeeks/QueueUsingStacks/solution.cpp:11–39

// 3. Push everything back to stack1.

struct Queue
{
    stack<int> s1;
    stack<int> s2;
    
    // oldest entered element is always at the top of stack 1
    void enque(int x)
    {
        s1.push(x);
    }
    
    // deQueue operation just pops from stack1
    int dequeue()
    {
        if(s1.empty())
            return 0;
        else
        {
            while(!s1.empty())
            {
                s2.push(s1.top());
                s1.pop();
            }
        }
        int x = s2.top();
        s2.pop();
        return x;
    }
};

int main()
{