12. Integer to Roman

class Solution {
    public String intToRoman(int num) {
        String[][] r=new String[][]{{"","M","MM","MMM"},
                        {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"},
                        {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"},
                        {"","I","II","III","IV","V","VI","VII","VIII","IX"}};
        return r[0][num/1000]+r[1][num%1000/100]+r[2][num%100/10]+r[3][num%10];
    }
}