RomanToInteger.java

class RomanToInteger {
    public int romanToInt(String s) {
        int prev = 0;
        int result = 0;
        for(int i = s.length() -1; i >= 0; i--) {
            char cur = s.charAt(i);
            int curVal = getInteger(cur);
            if(curVal < prev) {
                result -= curVal;
            } else {
                result += curVal;
            }
            prev = curVal;
        }
        return result;
    }
    private int getInteger(char c) {
        switch(c) {
            case 'I':
                return 1;
            case 'V':
                return 5;
            case 'X':
                return 10;
            case 'L':
                return 50;
            case 'C':
                return 100;
            case 'D':
                return 500;
            case 'M':
                return 1000;
        }
        return 0;        
    }
}