Integer to word conversion

Is there a library or a class/function that I can use to convert an integer to it’s verbal representation?

Example input:

4,567,788`

Example output:

Four million, Five hundred sixty-seven thousand, seven hundred eighty-eight

In case anyone wants a JavaScript version

Number.prototype.numberToWords = function () {
    var unitsMap = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"];
    var tensMap = ["zero", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"];

    var num = this.valueOf();
    if (Math.round(num == 0)) {
        return "zero";
    }
    if (num < 0) {
        var positivenum = Math.abs(num);
        return "minus " + Number(positivenum).numberToWords();
    }
    var words = "";
    if (Math.floor(num / 1000000) > 0) {
        words += Math.floor(num / 1000000).numberToWords() + " million ";
        num = Math.floor(num % 1000000);
    }
    if (Math.floor(num / 1000) > 0) {
        words += Math.floor(num / 1000).numberToWords() + " thousand ";
        num = Math.floor(num % 1000);
    }
    if (Math.floor(num / 100) > 0) {
        words += Math.floor(num / 100).numberToWords() + " hundred ";
        num = Math.floor(num % 100);
    }
    if (Math.floor(num > 0)) {
        if (words != "") {
            words += "and ";
        }
        if (num < 20) {
        words += unitsMap[num];
        }
        else {
            words += tensMap[Math.floor(num / 10)];
            if ((num % 10) > 0) {
                words += "-" + unitsMap[Math.round(num % 10)];
            }
        }
    }
    return words.trim();
}

answered Aug 8, 2014 at 5:38

Here is the spanish version:

        public static string numeroALetras(int number)
    {
        if (number == 0)
            return "cero";

        if (number < 0)
            return "menos " + numeroALetras(Math.Abs(number));

        string words = "";

        if ((number / 1000000) > 0)
        {
            words += numeroALetras(number / 1000000) + " millón ";
            number %= 1000000;
        }

        if ((number / 1000) > 0)
        {
            words += (number / 1000) == 1? "mil ": numeroALetras(number / 1000) + " mil ";
            number %= 1000;
        }
        if ((number / 100) == 1)
        {
            if (number == 100)
                words += "cien";
            else words += (number / 100)> 1? numeroALetras(number / 100) + " ciento ":"ciento ";
            number %= 100;
        }
        if ((number / 100) > 1)
        {
            var hundredMap = new[] {"","", "dosc", "tresc", "cuatroc", "quin", "seisc", "sietec", "ochoc", "novec" };
            if (number > 199)
                words += hundredMap[number/100] + "ientos ";
            else {
                words += numeroALetras(number / 100) + " ientos ";
            }
            number %= 100;
        }

        if (number > 0)
        {
            if (words != "")
                words += " ";

            var unitsMap = new[] { "cero", "uno", "dos", "tres", "cuatro", "cinco", "seis", "siete", "ocho", "nueve", "diez", "once", "doce", "trece", "catorce", "quince", "dieciseis", "diecisiete", "dieciocho", "diecinueve", "veinte" };
            var tensMap = new[] { "cero", "diez", "veinti", "treinta", "cuarenta", "cincuenta", "sesenta", "setenta", "ochenta", "noventa" };

            if (number < 21)
                words += unitsMap[number];
            else
            {                    
                words += tensMap[number / 10];
                if ((number % 10) > 0)
                    words += ((number % 10)>2?" y ": "") + unitsMap[number % 10];                    
            }
        }

        return words;
    }

answered Jun 1, 2017 at 15:12

Imports System.Text

Public Class NumberWriter

    Public Shared Function Parse(ByVal Number As String) As String
        If Not AreNumbers(Number) Then Return ""
        Dim TempQueue As New Queue(Of String)
        For Each ItemA As Char In Number.Replace(",", "").Reverse
            TempQueue.Enqueue(ItemA)
        Next
        Dim Blocks As New List(Of String)
        Dim BlockEmpty As New List(Of Boolean)
        Do
            Dim TempBlock As New StringBuilder(3)
            TempBlock.Append(TempQueue.Dequeue)
            If TempQueue.Count > 0 Then
                TempBlock.Append(TempQueue.Dequeue)
                If TempQueue.Count > 0 Then
                    TempBlock.Append(TempQueue.Dequeue)
                End If
            End If
            Blocks.Add(StrReverse(TempBlock.ToString))
            BlockEmpty.Add(TempBlock.ToString = "000")
            If TempQueue.Count < 1 Then Exit Do
        Loop
        Dim ResultStack As New Stack(Of String)
        For int1 As Integer = 0 To Blocks.Count - 1
            ResultStack.Push(ReadBlock(Blocks(int1)) & If(Not int1 = 0, If(Not BlockEmpty(int1), " " & CapitalizeWord(GetPlaceValueSet(int1)) & If(BlockEmpty(int1 - 1), "", ", "), ""), ""))
        Next
        Dim Result1 As String = ""
        Do Until ResultStack.Count < 1
            Result1 &= ResultStack.Pop
        Loop
        Return RemoveGrammarErrors(Result1)
    End Function

    Private Shared Function RemoveGrammarErrors(ByVal Str As String) As String
        Dim tstr As String = Str
        tstr.Replace("  ", " ")
        tstr.Replace(" , ", ", ")
        Return tstr
    End Function

    Private Shared Function AreNumbers(ByVal Str1 As String) As Boolean
        Dim Numbers() As String = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ","}
        For Each ItemA As Char In Str1
            Dim IsN As Boolean = False
            For Each ItemB As String In Numbers
                If ItemA = ItemB Then IsN = True
            Next
            If Not IsN Then
                Return False
            End If
        Next
        Return True
    End Function

    Private Shared Function ReadBlock(ByVal Block As String)
        Select Case Block.Length
            Case 1
                Return ReadSingleDigit(Block)
            Case 2
                Return ReadTwoDigits(Block)
            Case 3
                Return ReadThreeDigits(Block)
            Case Else
                Throw New Exception
        End Select
    End Function

    Private Shared Function ReadThreeDigits(ByVal Digits As String)
        If Digits.Length > 3 Then Throw New ArgumentException("There are too many digits.")
        Dim Result As String = ""
        If Not Digits(0) = "0" Then
            Result &= ReadSingleDigit(Digits(0)) & " Hundred "
        End If
        Result &= ReadTwoDigits(Digits.Substring(1))
        Return Result
    End Function

    Private Shared Function ReadTwoDigits(ByVal Digits As String)
        If Digits.Length > 2 Then Throw New ArgumentException("There are too many digits.")
        Select Case Digits(0)
            Case "0"
                Return ReadSingleDigit(Digits(1))
            Case "1"
                Return ReadTeenNumber(Digits)
            Case Else
                Return ReadFirstInNumberPair(Digits(0)) & If(Digits(1) = "0", "", "-" & ReadSingleDigit(Digits(1)))
        End Select
    End Function

    Private Shared Function ReadSingleDigit(ByVal Digit As String) As String
        If Not Digit.Length = 1 Then Throw New ArgumentException("There must be only one digit and it must be more than zero.")
        Select Case Digit
            Case "0"
                Return ""
            Case "1"
                Return "One"
            Case "2"
                Return "Two"
            Case "3"
                Return "Three"
            Case "4"
                Return "Four"
            Case "5"
                Return "Five"
            Case "6"
                Return "Six"
            Case "7"
                Return "Seven"
            Case "8"
                Return "Eight"
            Case "9"
                Return "Nine"
            Case Else
                Throw New Exception()
        End Select
    End Function

    Private Shared Function ReadTeenNumber(ByVal Num As String) As String
        Select Case Num
            Case "11"
                Return "Eleven"
            Case "12"
                Return "Twelve"
            Case "13"
                Return "Thirteen"
            Case "14"
                Return "Fourteen"
            Case "15"
                Return "Fifteen"
            Case "16"
                Return "Sixteen"
            Case "17"
                Return "Seventeen"
            Case "18"
                Return "Eighteen"
            Case "19"
                Return "Nineteen"
            Case Else
                Throw New Exception()
        End Select
    End Function

    Private Shared Function ReadFirstInNumberPair(ByVal Num As String) As String
        If Not (Num > 1 OrElse Num < 10) Then Throw New ArgumentException("Number must be more than 1 and less than 10")
        Select Case Num
            Case "2"
                Return "Twenty"
            Case "3"
                Return "Thirty"
            Case "4"
                Return "Fourty"
            Case "5"
                Return "Fifty"
            Case "6"
                Return "Sixty"
            Case "7"
                Return "Seventy"
            Case "8"
                Return "Eighty"
            Case "9"
                Return "Ninety"
            Case Else
                Throw New Exception()
        End Select
    End Function

    Private Shared Function CapitalizeWord(ByVal Word As String) As String
        Return Word.Substring(0, 1).ToUpper & Word.Substring(1)
    End Function

    Private Shared Function GetPlaceValueSet(ByVal Num As Byte) As String
        Select Case Num
            Case 0
                Return "" 'Hundreds
            Case 1
                Return "Thousand"
            Case 2
                Return "Million"
            Case 3
                Return "Billion"
            Case 4
                Return "Trillion"
            Case 5
                Return "Quadrillion"
            Case 6
                Return "Quintillion"
            Case 7
                Return "Sextillion"
            Case 8
                Return "Septillion"
            Case 9
                Return "Octillion"
            Case 10
                Return "Nonillion"
            Case 11
                Return "octillion"
            Case 12
                Return "nonillion"
            Case 13
                Return "decillion"
            Case 14
                Return "undecillion"
            Case 15
                Return "dodecillion,"
            Case 16
                Return "tredecillion"
            Case 17
                Return "quattuordecillion"
            Case 18
                Return "quindecillion"
            Case 19
                Return "sexdecillion"
            Case 20
                Return "septendecillion"
            Case 21
                Return "octodecillion"
            Case 22
                Return "novemdecillion"
            Case 23
                Return "vigintillion"
            Case 24
                Return "unvigintillion"
            Case 25
                Return "dovigintillion"
            Case 26
                Return "trevigintillion"
            Case 27
                Return "quattuorvigintillion"
            Case 28
                Return "quinvigintillion"
            Case 29
                Return "sexvigintillion"
            Case 30
                Return "septenvigintillion"
            Case 31
                Return "octovigintillion"
            Case 32
                Return "novemvigintillion"
            Case 33
                Return "trigintillion"
            Case 34
                Return "untrigintillion"
            Case 35
                Return "dotrigintillion"
            Case 36
                Return "tretrigintillion"
            Case 37
                Return "quattuortrigintillion"
            Case 38
                Return "quintrigintillion"
            Case 39
                Return "sextrigintillion"
            Case 40
                Return "septentrigintillion"
            Case 41
                Return "octotrigintillion"
            Case Else
                Throw New Exception
        End Select
    End Function
End Class

Sorry it’s in VB.NET, but it works completely. It is one way. Number to Verbal. Handles numbers up to 123 characters long I believe.

answered Sep 24, 2012 at 6:16

http://www.exchangecore.com/blog/convert-number-words-c-sharp-console-application/ has some C# script that looks to handle very large numbers and very small decimals.

using System;
using System.Collections.Generic;
using System.Text;

namespace NumWords
{
    class Program
    {
        // PROGRAM HANDLES NEGATIVE AND POSITIVE DOUBLES


        static String NumWordsWrapper(double n)
        {
            string words = "";
            double intPart;
            double decPart = 0;
            if (n == 0)
                return "zero";
            try {
                string[] splitter = n.ToString().Split('.');
                intPart = double.Parse(splitter[0]);
                decPart = double.Parse(splitter[1]);
            } catch {
                intPart = n;
            }

            words = NumWords(intPart);

            if (decPart > 0) {
                if (words != "")
                    words += " and ";
                int counter = decPart.ToString().Length;
                switch (counter) {
                    case 1: words += NumWords(decPart) + " tenths"; break;
                    case 2: words += NumWords(decPart) + " hundredths"; break;
                    case 3: words += NumWords(decPart) + " thousandths"; break;
                    case 4: words += NumWords(decPart) + " ten-thousandths"; break;
                    case 5: words += NumWords(decPart) + " hundred-thousandths"; break;
                    case 6: words += NumWords(decPart) + " millionths"; break;
                    case 7: words += NumWords(decPart) + " ten-millionths"; break;
                }
            }
            return words;
        }

        static String NumWords(double n) //converts double to words
        {
            string[] numbersArr = new string[] { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };
            string[] tensArr = new string[] { "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", "eighty", "ninty" };
            string[] suffixesArr = new string[] { "thousand", "million", "billion", "trillion", "quadrillion", "quintillion", "sextillion", "septillion", "octillion", "nonillion", "decillion", "undecillion", "duodecillion", "tredecillion", "Quattuordecillion", "Quindecillion", "Sexdecillion", "Septdecillion", "Octodecillion", "Novemdecillion", "Vigintillion" };
            string words = "";

            bool tens = false;

            if (n < 0) {
                words += "negative ";
                n *= -1;
            }

            int power = (suffixesArr.Length + 1) * 3;

            while (power > 3) {
                double pow = Math.Pow(10, power);
                if (n >= pow) {
                    if (n % pow > 0) {
                        words += NumWords(Math.Floor(n / pow)) + " " + suffixesArr[(power / 3) - 1] + ", ";
                    } else if (n % pow == 0) {
                        words += NumWords(Math.Floor(n / pow)) + " " + suffixesArr[(power / 3) - 1];
                    }
                    n %= pow;
                }
                power -= 3;
            }
            if (n >= 1000) {
                if (n % 1000 > 0) words += NumWords(Math.Floor(n / 1000)) + " thousand, ";
                else words += NumWords(Math.Floor(n / 1000)) + " thousand";
                n %= 1000;
            }
            if (0 <= n && n <= 999) {
                if ((int)n / 100 > 0) {
                    words += NumWords(Math.Floor(n / 100)) + " hundred";
                    n %= 100;
                }
                if ((int)n / 10 > 1) {
                    if (words != "")
                        words += " ";
                    words += tensArr[(int)n / 10 - 2];
                    tens = true;
                    n %= 10;
                }

                if (n < 20 && n > 0) {
                    if (words != "" && tens == false)
                        words += " ";
                    words += (tens ? "-" + numbersArr[(int)n - 1] : numbersArr[(int)n - 1]);
                    n -= Math.Floor(n);
                }
            }

            return words;

        }
        static void Main(string[] args)
        {
            Console.Write("Enter a number to convert to words: ");
            Double n = Double.Parse(Console.ReadLine());

            Console.WriteLine("{0}", NumWordsWrapper(n));
        }
    }
}

EDIT: brought code over from blog post

answered Jul 18, 2012 at 17:11

I was tasked to create a WEB API that converts numbers to words using C#.

Can be whole number or with decimal points in 48 hours time.

The call will be coming from a front-end application using Ajax Post method and return the converted result in the webpage.

I’ve publicly shared that project in the GitHub for reference: https://github.com/marvinglennlacuna/NumbersToWordsConverter.Api

With the following technical implementatation in placed:

1. MVC structured
2. API Controller
3. Service
4. Model
5. Error Handling
6. Unit Testing using MSTest
7. Code Coverage — 98%
8. Jquery

And with technical documentation about the following as well:

1. Purpose
2. Prerequisites
3. Functionl Requirements
4. Process Diagram and Output

**Result via Web Page (US-001) **

US-001 Convert Numbers to Words via web page process

US-001 Convert Numbers to Words via web page output

Result via Postman (US-002)

US-002 — Convert Numbers to Words via Postman process

US-002 — Convert Numbers to Words via Postman output

I think it’s just worth sharing a working solution in the case you need it for reference in interview/code test/school or for fun only.

Cheers,
Marvin

answered Oct 20, 2017 at 2:51

Here is my solution hope it will help you

namespace ConsoleApplication3
{

    class Program
    {


        static void Main(string[] args)
        {

            string s = Console.ReadLine();
            ConvertMyword(int.Parse(s));

            Console.Read();

        }

        static void ConvertMyword(int number)
        {
            int flag = 0;
            int lflag = 0;
            string words = String.Empty;
            string[] places = { "ones", "ten", "hundred", "thousand", "ten thousand", "lacs","tenlacs","crore","tencrore" };
            string rawnumber = number.ToString();
            char[] a = rawnumber.ToCharArray();
            Array.Reverse(a);
            for (int i = a.Length - 1; i >= 0; i--)
            {
                if (i % 2 == 0 && i > 2)
                {
                    if (int.Parse(a[i].ToString()) > 1)
                    {
                        if (int.Parse(a[i - 1].ToString()) == 0)
                        {
                            words = words + getNumberStringty(int.Parse(a[i].ToString())) + " " + places[i - 1] + " ";
                        }
                        else
                        {
                            words = words + getNumberStringty(int.Parse(a[i].ToString())) + " ";
                        }
                    }
                    else if (int.Parse(a[i].ToString()) == 1)
                    {
                        if (int.Parse(a[i - 1].ToString())== 0)
                        {
                            words = words +"Ten" + " ";
                        }
                        else
                        {
                            words = words + getNumberStringteen(int.Parse(a[i - 1].ToString())) + " ";
                        }
                        flag = 1;
                    }
                }
                else
                {
                    if (i == 1 || i == 0)
                    {
                        if (int.Parse(a[i].ToString()) > 1)
                        {
                            words = words + getNumberStringty(int.Parse(a[i].ToString())) + " " + getNumberString(int.Parse(a[0].ToString())) + " ";
                            break;
                        }
                        else if (int.Parse(a[i].ToString()) == 1)
                        {
                            if (int.Parse(a[i - 1].ToString()) == 0)
                            {
                                words = words + "Ten" + " ";
                            }
                            else
                            {
                                words = words + getNumberStringteen(int.Parse(a[i - 1].ToString())) + " ";
                            }

                            break;
                        }
                        else if (int.Parse(a[i - 1].ToString()) != 0)
                        {
                            words = words + getNumberString(int.Parse(a[i - 1].ToString())) + " ";
                            break;
                        }
                        else
                        {
                            break;
                        }
                    }
                    else
                    {
                        if (flag == 0)
                        {
                            for(int l=i;l>=0;l--)
                            {
                                if (int.Parse(a[l].ToString())!=0)
                                {
                                    lflag = 1;
                                }
                            }
                            if (lflag == 1 && int.Parse(a[i].ToString())!=0)
                            {

                                    words = words + getNumberString(int.Parse(a[i].ToString())) + " " + places[i] + " ";
                                    lflag = 0;


                            }
                            else if(lflag == 0)
                            {
                               // words = words + getNumberString(int.Parse(a[i].ToString())) + " " + places[i] + " ";
                                lflag = 0;
                                break;
                            }

                        }
                        else
                        {
                            words = words + " " + places[i] + " ";
                            flag = 0;
                        }

                    }
                }
            }
            Console.WriteLine(words);
        }
        static string getNumberString(int num)
        {
            string Word = String.Empty;
            switch (num)
            {
                case 1:
                    Word = "one";
                    break;
                case 2:
                    Word = "two";
                    break;

                case 3:
                    Word = "three";
                    break;

                case 4:
                    Word = "four";
                    break;

                case 5:
                    Word = "five";
                    break;

                case 6:
                    Word = "six";
                    break;
                case 7:
                    Word = "seven";
                    break;

                case 8:
                    Word = "eight";
                    break;

                case 9:
                    Word = "nine";
                    break;


            }
            return Word;
        }
        static string getNumberStringty(int num)
        {
            string Word = String.Empty;
            switch (num)
            {

                case 2:
                    Word = "twenty";
                    break;

                case 3:
                    Word = "thirty";
                    break;

                case 4:
                    Word = "fourty";
                    break;

                case 5:
                    Word = "fifty";
                    break;

                case 6:
                    Word = "sixty";
                    break;
                case 7:
                    Word = "seventy";
                    break;

                case 8:
                    Word = "eighty";
                    break;

                case 9:
                    Word = "ninty";
                    break;


            }
            return Word;
        }
        static string getNumberStringteen(int num)
        {
            string Word = String.Empty;
            switch (num)
            {
                    case 1:
                    Word = "eleven";
                    break;
                case 2:
                    Word = "tewlve";
                    break;

                case 3:
                    Word = "thirteen";
                    break;

                case 4:
                    Word = "fourteen";
                    break;

                case 5:
                    Word = "fifteen";
                    break;

                case 6:
                    Word = "sixteen";
                    break;
                case 7:
                    Word = "seventeen";
                    break;

                case 8:
                    Word = "eighteen";
                    break;

                case 9:
                    Word = "ninteen";
                    break;


            }
            return Word;
        }
    }

}

Though this is kind of old question, I have implemented this functionality with more detailed approach

public static class NumberToWord
    {
        private static readonly Dictionary<long, string> MyDictionary = new Dictionary<long, string>();

        static NumberToWord()
        {
            MyDictionary.Add(1000000000000000, "quadrillion");
            MyDictionary.Add(1000000000000, "trillion");
            MyDictionary.Add(1000000000, "billion");
            MyDictionary.Add(1000000, "million");
            MyDictionary.Add(1000, "thousand");
            MyDictionary.Add(100, "hundread");
            MyDictionary.Add(90, "ninety");
            MyDictionary.Add(80, "eighty");
            MyDictionary.Add(70, "seventy");
            MyDictionary.Add(60, "sixty");
            MyDictionary.Add(50, "fifty");
            MyDictionary.Add(40, "fourty");
            MyDictionary.Add(30, "thirty");
            MyDictionary.Add(20, "twenty");
            MyDictionary.Add(19, "nineteen");
            MyDictionary.Add(18, "eighteen");
            MyDictionary.Add(17, "seventeen");
            MyDictionary.Add(16, "sixteen");
            MyDictionary.Add(15, "fifteen");
            MyDictionary.Add(14, "fourteen");
            MyDictionary.Add(13, "thirteen");
            MyDictionary.Add(12, "twelve");
            MyDictionary.Add(11, "eleven");
            MyDictionary.Add(10, "ten");
            MyDictionary.Add(9, "nine");
            MyDictionary.Add(8, "eight");
            MyDictionary.Add(7, "seven");
            MyDictionary.Add(6, "six");
            MyDictionary.Add(5, "five");
            MyDictionary.Add(4, "four");
            MyDictionary.Add(3, "three");
            MyDictionary.Add(2, "two");
            MyDictionary.Add(1, "one");
            MyDictionary.Add(0, "zero");
        }

        /// <summary>
        /// To the verbal.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns></returns>
        public static string ToVerbal(this int value)
        {
            return ToVerbal((long) value);
        }

        /// <summary>
        /// To the verbal.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns></returns>
        public static string ToVerbal(this long value)
        {
            if (value == 0) return MyDictionary[value];

            if (value < 0)
                return $" negative {ToVerbal(Math.Abs(value))}";

            var builder = new StringBuilder();

            for (var i = 1000000000000000; i >= 1000; i = i/1000)
                value = ConstructWord(value, builder, i);

            value = ConstructWord(value, builder, 100);

            for (var i = 90; i >= 20; i = i - 10)
                value = ConstructWordForTwoDigit(value, builder, i);

            if (MyDictionary.ContainsKey(value))
                builder.AppendFormat("{0}" + MyDictionary[value], builder.Length > 0 
                    ? " " 
                    : string.Empty);

            return builder.ToString();
        }

        private static long ConstructWord(long value, StringBuilder builder, long key)
        {
            if (value >= key)
            {
                var unit = (int) (value/key);
                value -= unit*key;
                builder.AppendFormat(" {0} {1} " + MyDictionary[key], builder.Length > 0
                    ? ", "
                    : string.Empty, ToVerbal(unit));
            }
            return value;
        }
        private static long ConstructWordForTwoDigit(long value, StringBuilder builder, long key)
        {
            if (value >= key)
            {
                value -= key;
                builder.AppendFormat(" {0} " + MyDictionary[key], builder.Length > 0
                    ? " "
                    : string.Empty);
            }
            return value;
        } 
    }

FYI: i have user string interpolation which is only available in 4.6.1

answered Nov 23, 2016 at 14:38

New Method April 2022: To Convert Integers to Words in C#

Although a late answer, but in case someone arrives to this page after googling.

I have written the following C# function NumIntToWords(String NumIn) that provides a simple, short, and efficient method of converting integer numbers to words in C# complying with the US English Grammar Rules.

The function uses my devised method of SLST (Single Loop String Triplet).

Unlike other methods I had seen used here and elsewhere, the function has the following features:

• Simple, short, and fast.
• It does not use switch/case statements.
• It does require the use of extra spaces in strings or trimming strings.
• It does not use recursion.
• It does not use math functions (only one math for creating the string triplet).
• You can simply increase scale beyond Trillion by a simple increase of the
  scale array without any additional coding necessary.
• It compiles into a very shortcode.
• No extra libraries.

I have opted for the integer number to be converted to be passed as a string so you can handle very large integer numbers easily.

You can use it like this:

Console.WriteLine( NumIntToWords("1991345678974"));

\ Output:

One Trillion Nine Hundred Ninety-One Billion Three Hundred Forty-Five Million Six Hundred Seventy-Eight Thousand Nine Hundred Seventy-Four

C# SLST Function Method (c) Mohsen Alyafei:

/*********************************************************************
* @function    : NumIntToWords(String NumIn)
* @purpose     : Converts Unsigned Integers to Words
*                Using the SLST Method (C) Mohsen Alyafei 2019.
*                Does not check for Non-Numerics or +/- signs
* @version     : 2.11
* @author      : Mohsen Alyafei
* @Licence     : MIT
* @date        : 03 April 2022
* @in_param    : {NumIn} (Required): Number in string format
* @returns     : {string}: The number in English Words US Grammar
**********************************************************************/
public static string NumIntToWords(String NumIn) {
if (NumIn.TrimStart('0')=="") return "Zero";                   // If empty or zero return Zero

string[] T10s= {"","One","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Eleven","Twelve","Thirteen","Fourteen","Fifteen","Sixteen","Seventeen","Eighteen","Nineteen"},
         T20s= {"","","Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"},
       Scales= {"","Thousand","Million","Billion","Trillion"};// increase scale here (unlimited)
NumIn = new String('0', NumIn.Length * 2 % 3) + NumIn;        // Make it a String Triplet
String numToWords= "", wordTriplet, Triplet;

for (int digits = NumIn.Length; digits > 0; digits -= 3)  {   // Single Loop
    Triplet = NumIn.Substring(NumIn.Length - digits, 3);      // Get next Triplet
    if (Triplet != "000") {                                   // Convert Only if not empty
      wordTriplet="";
      int ScalePos= digits / 3 - 1,                           // Scale name position
              hund= int.Parse(""+Triplet[0]),
              tens= int.Parse(Triplet.Substring(1,2)),
              ones= int.Parse(""+Triplet[2]);
       wordTriplet= (hund>0 ? T10s[hund] + " Hundred" :"") +
                    (tens>0 && hund>0 ?" ":"") +
                    (tens<20 ? T10s[tens]: T20s[int.Parse(""+Triplet[1])]+(ones>0? "-"+T10s[ones]:"")) +
                    (ScalePos>0?" ":"")+ Scales[ScalePos];    // Add Scale Name to Triplet Word
       numToWords+= (numToWords!=""?" ":"") + wordTriplet;    // Concat Next Triplet Word
      }
}                   // Loop for the next Triplet
return numToWords;  // Return full Number in Words
}

answered Apr 4, 2022 at 18:31