原题地址：https://oj.leetcode.com/problems/integer-to-roman/
题意：
Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.
解题思路：整数（1~3999）到罗马数字的转换。字母前置表示减法，例如CM表示M-C=1000-100=900，XL表示L-X=50-10=40。
代码：
class Solution: # @return a string def intToRoman(self, num): values = [ 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 ] numerals = [ "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" ] list = ‘‘ for i in range(0, len(values)): while num >= values[i]: num -= values[i] list += numerals[i] return list