12. 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 String intToRoman(int num) {
if(num <= 0) {
return "";
}
int[] nums = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
String[] symbols = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
StringBuilder res = new StringBuilder();
int digit=0;
while (num > 0) {
int times = num / nums[digit];
num -= nums[digit] * times;
for ( ; times > 0; times--) {
res.append(symbols[digit]);
}
digit++;
}
return res.toString();
}