roman_numerals_decoder.cs

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

public class RomanDecode
{
    public static int Solution(string roman)
    {
        // Hashtable representing the numeric value of each roman numeral key
        Hashtable romanKeys = new Hashtable() {
            {'I', 1},
            {'V', 5},
            {'X', 10},
            {'L', 50},
            {'C', 100},
            {'D', 500},
            {'M', 1000}
        };

        // If roman is one numeral, return numeric value
        if (roman.Length == 1)
        {
            return (int)romanKeys[roman.ToCharArray()[0]];
        }
        else
        {
            // Array of chars in roman in reverse order
            char[] romanChars = roman.ToCharArray();
            Array.Reverse(romanChars);

            // Numeric value of roman
            int total = 0;

            // Loop over each numeral in romanChars
            for (int i = 0; i < romanChars.Length; i++)
            {
                if (i == romanChars.Length - 1)
                {
                    total += ((int)romanKeys[romanChars[i]]);
                }
                else
                {
                    // If the numeral at the following index is less than the current numeral, subtract them, and add result to total
                    if ((int)romanKeys[romanChars[i + 1]] < (int)romanKeys[romanChars[i]])
                    {
                        total += ((int)romanKeys[romanChars[i]] - (int)romanKeys[romanChars[i + 1]]);
                        i += 1;
                    }
                    else
                    {
                        total += ((int)romanKeys[romanChars[i]]);
                    }
                }
            }
            return total;
        }
        throw new NotImplementedException();
    }
}