Converting integers to roman numerals

Question

I\'m trying to write a function that converts numbers to roman numerals. This is my code so far; however, it only works with numbers that are less than 400. Is there a quick

Answer 1

The solution is lengthy, but easy to understand for a beginner. Process up to 3000

namespace RomansTranslator
{
    using System;
    using System.Collections.Generic;
    /// <summary>
    /// Accepts a number (between 1 and 3000) and prints its Roman equivalent.
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            string number = string.Empty;
            Console.Write("Enter the Numeric number : ");
            number = Console.ReadLine();
            if (IsValid(number)) // Validates the input
            {
                string roman = ConvertToRoman(number);
                Console.WriteLine("Roman Number is " + roman);
            }
            else
            {
                Console.WriteLine("Invalid Number");
            }
            Console.ReadKey();
        }

        private static string ConvertToRoman(string numberString)
        {
            string romanValue = string.Empty;
            int number = Convert.ToInt32(numberString);
            if (number >= 1)
            {
                // Loop through each roman character from highest 
                foreach (int item in RomanDictionary().Keys)
                {
                    while (number >= item)
                    {
                        romanValue = romanValue + RomanString(item);
                        number -= item;
                    }
                }
            }
            return romanValue;
        }

        /// <summary>
        /// Returns Roman Equvalent
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        private static string RomanString(int n)
        {
            string romanString = string.Empty;
            romanString = RomanDictionary()[n].ToString();
            return romanString;
        }

        /// <summary>
        /// List of Roman Characters 
        /// </summary>
        /// <returns></returns>
        private static Dictionary<int, string> RomanDictionary()
        {

            Dictionary<int, string> romanDic = new Dictionary<int, string>();
            romanDic.Add(1000, "M");
            romanDic.Add(900, "CM");
            romanDic.Add(500, "D");
            romanDic.Add(400, "CD");
            romanDic.Add(100, "C");
            romanDic.Add(90, "XC");
            romanDic.Add(50, "L");
            romanDic.Add(40, "XL");
            romanDic.Add(10, "X");
            romanDic.Add(9, "IX");
            romanDic.Add(5, "V");
            romanDic.Add(4, "IV");
            romanDic.Add(1, "I");
            return romanDic;
        }


        /// <summary>
        /// Validates the Input
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        private static bool IsValid(string input)
        {
            int value = 0;
            bool isValid = false;
            if (int.TryParse(input, out value))
            {
                if (value <= 3000)
                {
                    isValid = true;
                }
            }
            return isValid;
        }
    }
}

Answer 2

Here is a slim solution from DotNetSnippets

private string ToRomanNumber(int number)
{
    StringBuilder result = new StringBuilder();
    int[] digitsValues = { 1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000 };
    string[] romanDigits = { "I", "IV", "V", "IX", "X", "XL", "L", "XC", "C", "CD", "D", "CM", "M" };
    while (number > 0)
    {
        for (int i = digitsValues.Count() - 1; i >= 0; i--)
            if (number / digitsValues[i] >= 1)
            {
                number -= digitsValues[i];
                result.Append(romanDigits[i]);
                break;
            }
    }
    return result.ToString();
}

Answer 3

I can provide a method which is comparatively simpler than the existing

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
public class Form1
{
    int[] indx = {
        1,
        2,
        3,
        4,
        5,
        10,
        50,
        100,
        500,
        1000
        // initialize array of integers 
    };
    string[] row = {
        "I",
        "II",
        "III",
        "IV",
        "V",
        "X",
        "L",
        "C",
        "D",
        "M"
        //Carasponding roman letters in for the numbers in the array
    };
        // integer to indicate the position index for link two arrays 
    int limit = 9;
        //string to store output
    string output = "";
    private void Button1_Click(System.Object sender, System.EventArgs e)
    {
        int num = 0;
        // stores the input 
        output = "";
        // clear output before processing
        num = Convert.ToInt32(txt1.Text);
        // get integer value from the textbox
        //Loop until the value became 0
        while (num > 0) {
            num = find(num);
            //call function for processing
        }
        txt2.Text = output;
        // display the output in text2
    }
    public int find(int Num)
    {
        int i = 0;
        // loop variable initialized with 0
        //Loop until the indx(i).value greater than or equal to num
        while (indx(i) <= Num) {
            i += 1;
        }
        // detemine the value of limit depends on the itetration
        if (i != 0) {
            limit = i - 1;
        } else {
            limit = 0;
        }
        output = output + row(limit);
        //row(limit) is appended with the output
        Num = Num - indx(limit);
        // calculate next num value
        return Num;
        //return num value for next itetration 
    }
}

Answer 4

@Backwards_Dave You wanted a solution that goes to max number, here you go:

public class ConvertDecimalNumberToRomanNumberType
{
    public class RomanNumberType
    {
        public string RomanNumber;
        public int RomanNumberValue;
    }

    public List<RomanNumberType> RomanNumbers;

    public void Initialize()
    {
        RomanNumbers = new List<RomanNumberType>();

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "M", RomanNumberValue = 1000 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "CM", RomanNumberValue = 900 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "D", RomanNumberValue = 500 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "CD", RomanNumberValue = 400 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "C", RomanNumberValue = 100 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "XC", RomanNumberValue = 90 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "L", RomanNumberValue = 50 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "XL", RomanNumberValue = 40 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "X", RomanNumberValue = 10 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "IX", RomanNumberValue = 9 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "V", RomanNumberValue = 5 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "IV", RomanNumberValue = 4 });

        RomanNumbers.Add(new RomanNumberType() { RomanNumber = "I", RomanNumberValue = 1 });
    }

    public string ConvertDecimalNumberToRomanNumber(int GetConvertDecimalNumberToRomanNumber)
    {
        string
            FunctionResult
            , CurrentRomanNumber = "";

        int
            FunctionGet = GetConvertDecimalNumberToRomanNumber
            , DecimalNumberRemaining = FunctionGet;

        foreach(RomanNumberType RomanNumber in RomanNumbers)
            while(RomanNumber.RomanNumberValue <= DecimalNumberRemaining)
            {
                DecimalNumberRemaining -= RomanNumber.RomanNumberValue;

                CurrentRomanNumber += RomanNumber.RomanNumber;
            }

        FunctionResult = CurrentRomanNumber;

        return FunctionResult;
    }
}

usage :

ConvertDecimalNumberToRomanNumberType ConvertDecimalNumberToRomanNumberObject = new ConvertDecimalNumberToRomanNumberType();

ConvertDecimalNumberToRomanNumberObject.Initialize();

var SomeVariable = ConvertDecimalNumberToRomanNumberObject.ConvertDecimalNumberToRomanNumber(1999);

Answer 5

Here's a much simpler algorithm - forgive me, I don't know C# so I'm writing this in JavaScript, but the same algorithm should apply (and I've commented so you can understand the algorithm):

function intToRoman(int) {

    // create 2-dimensional array, each inner array containing 
    // roman numeral representations of 1-9 in each respective 
    // place (ones, tens, hundreds, etc...currently this handles
    // integers from 1-3999, but could be easily extended)
    var romanNumerals = [
        ['', 'i', 'ii', 'iii', 'iv', 'v', 'vi', 'vii', 'viii', 'ix'], // ones
        ['', 'x', 'xx', 'xxx', 'xl', 'l', 'lx', 'lxx', 'lxxx', 'xc'], // tens
        ['', 'c', 'cc', 'ccc', 'cd', 'd', 'dc', 'dcc', 'dccc', 'cm'], // hundreds
        ['', 'm', 'mm', 'mmm'] // thousands
    ];

    // split integer string into array and reverse array
    var intArr = int.toString().split('').reverse(),
        len = intArr.length,
        romanNumeral = '',
        i = len;

    // starting with the highest place (for 3046, it would be the thousands 
    // place, or 3), get the roman numeral representation for that place 
    // and append it to the final roman numeral string
    while (i--) {
        romanNumeral += romanNumerals[ i ][ intArr[i] ];
    }

    return romanNumeral;

}

console.log( intToRoman(3046) ); // outputs mmmxlvi

Answer 6

This should be the simplest solution.

public string IntToRoman(int num)
{
    var result = string.Empty;
    var map = new Dictionary<string, int>
    {
        {"M", 1000 },
        {"CM", 900},
        {"D", 500},
        {"CD", 400},
        {"C", 100},
        {"XC", 90},
        {"L", 50},
        {"XL", 40},
        {"X", 10},
        {"IX", 9},
        {"V", 5},
        {"IV", 4},
        {"I", 1}
    };
    foreach (var pair in map)
    {
        result += string.Join(string.Empty, Enumerable.Repeat(pair.Key, num / pair.Value));
        num %= pair.Value;
    }
    return result;
}