public class Solution {

     private static char[][] chars = {{'I', 'V'}, {'X', 'L'}, {'C', 'D'}, {'M', 'O'}};

     private static HashMap<Character, Integer> map = null;

     private static void init() {

         map = new HashMap<Character, Integer>();

         for (int i = 0; i < 4; i++) {

             map.put(chars[i][0], (int) Math.pow(10, i));

             map.put(chars[i][1], 5 * (int) Math.pow(10, i));

         }

     }

     public static int romanToInt(String s) {

         if (map == null) {

             init();

         }

         int length = s.length();

         int result = 0;

         boolean flag = true;

         int prev = map.get(s.charAt(0));

         for (int i = 1; i < length; i++) {

             int x = map.get(s.charAt(i));

             if (prev >= x) {

                 result += prev;

             } else {

                 result -= prev;

             }

             prev = x;

         }

         result += prev;

         return result;

     }

 }