using System;

public class Program

{

// 1. Implement Reverse method

// 2. Implement MyCustomQueue methods

// 3. Implement MyCustomStack methods

// ALL Console.WriteLine must return True

// DON'T use Stack<T> or Queue<T> just plain collection.

    public static void Main()

    {

        var ex1 = "tset";

        var ex2 = "121";

        var ex3 = "321";

        Console.WriteLine(Reverse("test") == ex1);

        Console.WriteLine(Reverse("121") == ex2);

        Console.WriteLine(Reverse("111") == ex2);

        Console.WriteLine(Reverse("123") == ex3);

        IMyCustomQueueFIFO queue = new MyCustomQueue();

        queue.Push(1);

        queue.Push(2);

        Console.WriteLine(queue.Pop() == 1);

        Console.WriteLine(queue.Pop() == 2);

        IMyCustomStackLIFO stack = new MyCustomStack(); 

        stack.Push(1);

        stack.Push(2);

        Console.WriteLine(stack.Pop() == 2);

        Console.WriteLine(stack.Pop() == 1);

    }

    private static string Reverse(string arg) 

    {

        // IMPLEMENT ME but don't use built in method

        return "";

    }

}

​

// First In - First Out

interface IMyCustomQueueFIFO {

    void Push(int num); // insert item

    int Pop(); // gets and removes item

}

​

// Last In - First Out

interface IMyCustomStackLIFO {

    void Push(int num); // insert item

    int Pop(); // gets and removes item

}

​

class MyCustomQueue : IMyCustomQueueFIFO {

    public void Push(int num) {

        throw new NotImplementedException();

    }

    public int Pop() {

        throw new NotImplementedException();

    }

}

​

class MyCustomStack : IMyCustomStackLIFO {

    public void Push(int num) {

        throw new NotImplementedException();

    }

    public int Pop() {

        throw new NotImplementedException();

    }

}