FruitBatInShades Code

public class NumberToWords
	{
		// Single-digit and small number names
		private string[] _smallNumbers = new string[] { "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen" };
 
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		// Tens number names from twenty upwards
		private string[] _tens = new string[] { "", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety" };
 
		// Scale number names for use during recombination
		private string[] _scaleNumbers = new string[] { "", "Thousand", "Million", "Billion" };
 
 
 
		// Converts an integer value into English words
		public string ToWords(int number)
		{
			// Zero rule
			if (number == 0)
				return _smallNumbers[0];
 
			// Array to hold four three-digit groups
			int[] digitGroups = new int[4];
 
			// Ensure a positive number to extract from
			int positive = Math.Abs(number);
 
			// Extract the three-digit groups
			for (int i = 0; i < 4; i++)
			{
				digitGroups[i] = positive % 1000;
				positive /= 1000;
			}
 
			// Convert each three-digit group to words
			string[] groupText = new string[4];
 
			for (int i = 0; i < 4; i++)
				groupText[i] = ThreeDigitGroupToWords(digitGroups[i]);
 
			// Recombine the three-digit groups
			string combined = groupText[0];
			bool appendAnd;
 
			// Determine whether an 'and' is needed
			appendAnd = (digitGroups[0] > 0) && (digitGroups[0] < 100);
 
			// Process the remaining groups in turn, smallest to largest
			for (int i = 1; i < 4; i++)
			{
				// Only add non-zero items
				if (digitGroups[i] != 0)
				{
					// Build the string to add as a prefix
					string prefix = groupText[i] + " " + _scaleNumbers[i];
 
					if (combined.Length != 0)
						prefix += appendAnd ? " and " : ", ";
 
					// Opportunity to add 'and' is ended
					appendAnd = false;
 
					// Add the three-digit group to the combined string
					combined = prefix + combined;
				}
			}
 
			// Negative rule
			if (number < 0)
				combined = "Negative " + combined;
 
			return combined;
		}
 
 
 
		// Converts a three-digit group into English words
		private string ThreeDigitGroupToWords(int threeDigits)
		{
			// Initialise the return text
			string groupText = "";
 
			// Determine the hundreds and the remainder
			int hundreds = threeDigits / 100;
			int tensUnits = threeDigits % 100;
 
			// Hundreds rules
			if (hundreds != 0)
			{
				groupText += _smallNumbers[hundreds] + " Hundred";
 
				if (tensUnits != 0)
					groupText += " and ";
			}
 
			// Determine the tens and units
			int tens = tensUnits / 10;
			int units = tensUnits % 10;
 
			// Tens rules
			if (tens >= 2)
			{
				groupText += _tens[tens];
				if (units != 0)
					groupText += " " + _smallNumbers[units];
			}
			else if (tensUnits != 0)
				groupText += _smallNumbers[tensUnits];
 
			return groupText;
		}
	}
 
}