Integer to Roman

Given an integer, convert it to a roman numeral.

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

public class Solution {
    public String intToRoman(int num) {
        String[] romans = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
        int[] values = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
        if (num<0||num>3999) {
            return null;
        }
        if (num==0) {
            return "";
        }
        String result = new String();
        int i=0;
        while (num>0) {
            while (num>=values[i]){
                //按照values的顺做贪心
                result += romans[i];
                num -= values[i];
            }
            i++;
        }
        return result;
    }
}