题目：
https://leetcode-cn.com/problems/integer-to-roman/
答案： 贪心算法
public String intToRoman(int num) {
StringBuilder stringBuilder = new StringBuilder();
int[] keys = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5,4 ,1};
String[] values = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
int index = 0;
while (index < 13) {
while (num >= keys[index]) {
stringBuilder.append(values[index]);
num -= keys[index];
}
index++;
}
return stringBuilder.toString();
}