12. 整数转罗马数字

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