13. Roman to Integer

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

思路：反正不会考

public class Solution {
    public int romanToInt(String s) {
              int decimal = 0;
        int lastNumber = 0;


        /* operation to be performed on upper cases even if user 
           enters roman values in lower case chars */
        for (int x = s.length() - 1; x >= 0 ; x--) {
            char convertToDecimal = s.charAt(x);
            // System.out.println(convertToDecimal);
            switch (convertToDecimal) {
                case 'M':
                    decimal = processDecimal(1000, lastNumber, decimal);
                    lastNumber = 1000;
                    break;

                case 'D':
                    decimal = processDecimal(500, lastNumber, decimal);
                    lastNumber = 500;
                    break;

                case 'C':
                    decimal = processDecimal(100, lastNumber, decimal);
                    lastNumber = 100;
                    break;

                case 'L':
                    decimal = processDecimal(50, lastNumber, decimal);
                    lastNumber = 50;
                    break;

                case 'X':
                    decimal = processDecimal(10, lastNumber, decimal);
                    lastNumber = 10;
                    break;

                case 'V':
                    decimal = processDecimal(5, lastNumber, decimal);
                    lastNumber = 5;
                    break;

                case 'I':
                    decimal = processDecimal(1, lastNumber, decimal);
                    lastNumber = 1;
                    break;
            }
        }
        return decimal;
    }

    public static int processDecimal(int decimal, int lastNumber, int lastDecimal) {
        if (lastNumber > decimal) {
            return lastDecimal - decimal;
        } else {
            return lastDecimal + decimal;
        }
    }

}