using System;

using System.Text;

using System.Collections.Generic;

​

public class Program

{

    /// <summary>

    /// Write out a dollar value in words. Handles positive values less

    /// than $1,000, and up to two decimal places.

    /// </summary>

    static string DollarsToWords(decimal value)

    {

        if (value < 0 || value >= 1000)

            throw new ArgumentOutOfRangeException(nameof(value));

        if (value == 0) return "zero dollars";

​

        var output = new StringBuilder();

        var dollars = (int) value;

        var cents = (int) ((value - dollars) * 100);

        if (dollars > 0)

        {

            IntToWords(dollars, output);

            output.Append(" dollar");

            if (dollars > 1)

                output.Append("s");

            if (cents > 0)

                output.Append(" and ");

        }

​

        if (cents > 0)

        {

            IntToWords(cents, output);

            output.Append(" cent");

​

            if (cents > 1)

                output.Append("s");

        }

        return output.ToString();

    }

    /// <summary>

    /// Write out an integer values in words. Handles positive values less than 1000.

    /// </summary>

    static void IntToWords(int value, StringBuilder output)

    {

        if (NamedNumbers.TryGetValue(value, out var name))

        {

            output.Append(name);

            return;

        }

        if (value >= 100)

        {

            var lower = value % 100;

            var upper = (value - lower) / 100;

​

            IntToWords(upper, output);

            output.Append(" hundred");

            if (lower > 0)

            {

                output.Append(" and ");

                IntToWords(lower, output);

            }

        }

        else

        {

            var lower = value %10;

            var upper = value - lower;

​

            IntToWords(upper, output);

            if (lower > 0)

            {

                output.Append(" ");

                IntToWords(lower, output);

            }

        }

    }

    static Dictionary<int, string> NamedNumbers = new Dictionary<int, string>

    {

        { 0, "zero" },

        { 1, "one" },

        { 2, "two" },

        { 3, "three" },

        { 4, "four" },

        { 5, "five" },

        { 6, "six" },

        { 7, "seven" },

        { 8, "eight" },

        { 9, "nine" },

        { 10, "ten" },

        { 11, "eleven" },

        { 12, "twelve" },

        { 13, "thirteen" },

        { 14, "fourteen" },

        { 15, "fifteen" },

        { 16, "sixteen" },

        { 17, "seventeen" },

        { 18, "eighteen" },

        { 19, "nineteen" },

        { 20, "twenty" },

        { 30, "thirty" },

        { 40, "fourty" },

        { 50, "fifty" },

        { 60, "sixty" },

        { 70, "seventy" },

        { 80, "eighty" },

        { 90, "ninety" }

    };

    public static void Main()

    {

        Test(0, "zero dollars");

        Test(1, "one dollar");

        Test(1.01m, "one dollar and one cent");

        Test(1.63m, "one dollar and sixty three cents");

        Test(4, "four dollars");

        Test(0.12m, "twelve cents");

        Test(10.55m, "ten dollars and fifty five cents");

        Test(77.01m, "seventy seven dollars and one cent");

        Test(70.40m, "seventy dollars and fourty cents");

        Test(120, "one hundred and twenty dollars");

        Test(999.99m, "nine hundred and ninety nine dollars and ninety nine cents");

    }

​

    static void Test(decimal number, string expected)

    {

        var actual = DollarsToWords(number);

        if (actual == expected)

        {

            Console.WriteLine($"{number}: PASS");

            return;

        }

        Console.WriteLine($"{number}: FAIL");

        Console.WriteLine($"  Expected: {expected}");

        Console.WriteLine($"  Actual:   {actual}");

        Console.WriteLine();

    }

}