12.md

class Solution:
    def intToRoman(self, num: int) -> str:
        romanNum = ["I","IV","V","IX","X","XL","L","XC","C","CD","D","CM","M"]
        numeral =  [1,4,5,9,10,40,50,90,100,400,500,900,1000]
        if num < 1 or num > 3999:
            return 0
        res, i = "", len(romanNum) -1
        while num > 0:
            if num - numeral[i] >= 0:
                res += romanNum[i]
                num -= numeral[i]
            else:
                i -= 1
        return res

同样的运行速度，另一种描述方式：

class Solution:
    def intToRoman(self, num: int) -> str:
        romanNum = ["I","IV","V","IX","X","XL","L","XC","C","CD","D","CM","M"]
        numeral =  [1,4,5,9,10,40,50,90,100,400,500,900,1000]
        if num < 1 or num > 3999:
            return 0
        res = ""
        for i in list(range(len(romanNum)))[::-1]:
            while numeral[i] <= num:
                res += romanNum[i]
                num -= numeral[i]
        return res