13.RomantoInteger（整数转罗马数字）

Given a roman numeral, convert it to an integer.

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

题目大意：给定[1,3999]之间的某个整数，将其转为罗马数字。

解题思路：代码如下：（93ms，beats 75.93%）

public class Solution {
    public String intToRoman(int num) {
        int[] ints = new int[]{
1000,
900,500,400,100,
90,50,40,10,
9,5,4,1
};
String[] romans = new String[]{
"M", 
"CM", "D", "CD", "C", 
"XC", "L", "XL", "X", 
"IX", "V", "IV", "I" 
};
StringBuilder sb = new StringBuilder();
int index = 0;
while(num>0){
if(num-ints[index]>=0){
num-=ints[index];
sb.append(romans[index]);
}
else
index++;
}
return sb.toString();
    }
}