using System;

using System.Collections.Concurrent;

using System.Globalization;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Assert.AreEqual(1, Scale(1, 0), "Invariant scale failed");

        Assert.AreEqual(0, Scale(0, 100), "Scale of 0 failed");

        Assert.AreEqual(100, Scale(1, 2), "Scale(1, 2) failed");

        Assert.AreEqual(0.01m, Scale(1, -2), "Scale(1, -2) failed");

        Assert.AreEqual(1, Scale(0.01m, 2), "Scale(0.01, 2) failed");

        Assert.AreEqual(1, Scale(100, -2), "Scale(100, -2) failed");

        var large = Scale(1, 28);

        var small = Scale(1, -28);

        var shouldBeLarge = Scale(small, 56);

        var shouldBeSmall = Scale(large, -56);

        Assert.AreEqual(large, shouldBeLarge, "scaling 1e-28 by 56 failed");

        Assert.AreEqual(small, shouldBeSmall, "scaling 1e28 by -56 failed");

        Console.WriteLine("All tests passed");

    }

    private static ConcurrentDictionary<int, decimal> powersOfTen = new ConcurrentDictionary<int, decimal>();

​

    /// <summary>

    /// Scales value to move the decimal point by a certain number of places

    /// </summary>

    public static decimal Scale(decimal value, int places)

    {

        // handle degenerate case

        if ( value == 0 )

            return 0;

        // handle the case when the power of ten will overflow

        if ( Math.Abs(places) > 28 )

        {

            var intermediateNumberOfPlaces = places / 2;

            var intermediateValue = Scale(value, intermediateNumberOfPlaces);

            return Scale(intermediateValue, places - intermediateNumberOfPlaces);

        }

        // normal cases

        var powerOfTen = getPowerOfTen(Math.Abs(places));

        if ( places > 0 )

            return value * powerOfTen;

        return value / powerOfTen;

    }

    private static decimal getPowerOfTen(int power)

    {

        return powersOfTen.GetOrAdd(power, p =>

                                    {

                                        var powerAsString = "1" + string.Concat(Enumerable.Repeat("0", p));

                                        return decimal.Parse(powerAsString, CultureInfo.InvariantCulture);

                                    });

    }

    public static class Assert

    {

        public static void AreEqual(decimal expected, decimal actual, string message)

        {

            if( expected!= actual )

                throw new Exception(message);

        }

    }

}