using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

using System.Text;

using System.Threading.Tasks;

​

namespace leetcode

{

    public class Solution

    {

        Dictionary<string, int> romanNumbers = new Dictionary<string, int>();

        int FinalNum = 0;

        public int RomanToInt(string s)

        {

            romanNumbers.Add("I", 1);

            romanNumbers.Add("V", 5);

            romanNumbers.Add("X", 10);

            romanNumbers.Add("L", 50);

            romanNumbers.Add("C", 100);

            romanNumbers.Add("D", 500);

            romanNumbers.Add("M", 1000);

            for (int i=0; i < s.Length; i++) //IV

            {

                if (s[i] == 'I' && s[i] != s.Last() && ((s[i + 1] == 'V') || (s[i + 1] == 'X')))

                {

​

                    switch (s[i+1])

                    {

                        case 'V':

                            FinalNum += 4;

                            i++;

                            break;

                        case 'X':

                            FinalNum += 9;

                            i++;

                            break;

                    }

                }

                else if (s[i] == 'X' && s[i] != s.Last() && ((s[i + 1] == 'L') || (s[i + 1] == 'C')))

                {

​

                    switch (s[i + 1])

                    {

                        case 'L':

                            FinalNum += 40;

                            i++;

                            break;

                        case 'C':

                            FinalNum += 90;

                            i++;

                            break;

                    }

                }

                else if (s[i] == 'C' && s[i] != s.Last() && ((s[i + 1] == 'D') || (s[i + 1] == 'M')))

                {

​

                    switch (s[i + 1])

                    {

                        case 'D':

                            FinalNum += 400;

                            i++;

                            break;

                        case 'M':

                            FinalNum += 900;

                            i++;

                            break;

                    }

                }

                else

                {

                    FinalNum += turnRomanCharToInt(s[i]);

                }

​

            }

            Console.WriteLine(FinalNum);

            return FinalNum;

        }

​

        public int turnRomanCharToInt(char ch)

        {

            var myKey = romanNumbers.FirstOrDefault(x => x.Key == ch.ToString()).Value;

            return myKey;

        }

        public static void Main()

        {

            string s = "MMCCCXCIX"; //my:2419 real:2399 2000+100+100+100+90(XC)+9(IX)

            Solution solution = new Solution();

            solution.RomanToInt(s);

        }

    }

}

​