romanToInt-1

public class Solution {
    public int romanToInt(String s) {
        s = s.toLowerCase();
        int i = 0;
        int total = 0;
        while (i < s.length() - 1) {
            int a = romanValue(s.charAt(i));
            int b = romanValue(s.charAt(i+1));
            if (b > a) {
                total += b - a;
                i += 2;
            } else {
                total += a;
                i++;
            }
        }
        if (i < s.length())
            total += romanValue(s.charAt(s.length() - 1));
        return total;
    }

    private int romanValue(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;
    }
}