using System;

​

public static class NumberExtensions

{

    public static bool IsPowerOf2(this long input)

    {

        if (input <= 0)

        {

            return false;

        }

        while (input > 1)

        {

            if (input % 2 == 1)

            {

                return false;

            }

            input /= 2;

        }

        return true;

    }

    public static bool IsPowerOf2Alt(this long input)

    {

        if (input <= 0)

        {

            return false;

        }

        long count = input - ((input >> 1) & 033333333333) - ((input >> 2) & 011111111111);

        return ((count + (count >> 3)) & 030707070707) % 63 == 1;

    }

}

​

class Program

{

    private static readonly (long Input, bool Expected)[] Cases =

    {

        (-1, false),

        (0, false),

        (1, true),

        (2, true),

        (4, true),

        (6, false),

        (128, true),

        (4294967296, true)

    };

    static void Main()

    {

        RunTests(NumberExtensions.IsPowerOf2);

    }

    static void RunTests(Func<long, bool> method)

    {

        foreach (var test in Cases)

        {

            try

            {

                var actual = method(test.Input);

                var result = actual.Equals(test.Expected);

​

                if (result)

                {

                    Console.WriteLine($"\"{test.Input}\": OK");

                }

                else

                {

                    Console.WriteLine($"\"{test.Input}\": Fail (expected: \"{test.Expected}\", actual: \"{actual}\")");

                }

            }

            catch (Exception ex)

            {

                Console.WriteLine($"\"{test.Input}\": Fail with exception:\r\n{ex}");

            }

        }

    }

}