#codingexercise
int RomanToInt(string s)
{
 if (String.IsNullOrEmpty(s)) return 0;
//regex match string with +[IVXLCDM]
  var dict = new Dictionary<char, int> ();
        dict['I'] = 1;
        dict['V'] = 5;
        dict['X'] = 10;
        dict['L'] = 50;
        dict['C'] = 100;
        dict['D'] = 500;
        dict['M'] = 1000;
   int ret = 0;
   char temp;

   stack<char> st;
   st.push(s[0]);

  for (int I = 1; I< s.Length; I++)
  {
    if (st.count > 0 && dict[s[I]] > dict[st.Peek()])
    {
        temp = st.top();
        st.pop();
        ret = ret - dict[temp];
       st.Push(s[I]);
    }
    else
      st = st.Push(s[I]);
  }

while(!st.empty)
{
 ret += m[ st.Peek()];
 st.pop();

}
 return ret;
}
// there are other ways of doing this but I'm just listing the earliest one.

int RomanToInt(string s, int index, Dictionary<char, int> dict)
{
// validate s as not empty, not null and roman numerals only
 if (index == s.length) return 0;
 if (index - 1 > 0 && dict[s[index]] > dict[s[index-1]])
     return (0-2 * dict[s[Index-1]]) + dict[s[Index]] + RomanToInt(s, index+1, dict);
else
    return dict[s[Index]] + RomanToInt(s, index + 1, dict);
}