字符          数值
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

    I 可以放在 V (5) 和 X (10) 的左边，来表示 4 和 9。X 可以放在 L (50) 和 C (100) 的左边，来表示 40 和 90。 C 可以放在 D (500) 和 M (1000) 的左边，来表示 400 和 900。

输入: 3
输出: "III"

输入: 4
输出: "IV"

输入: 9
输出: "IX"

输入: 58
输出: "LVIII"
解释: L = 50, V = 5, III = 3.

输入: 1994
输出: "MCMXCIV"
解释: M = 1000, CM = 900, XC = 90, IV = 4.

class Solution(object):def intToRoman(self, num):""":type num: int:rtype: str"""def num_rom(a, base):dict_num_rom = {1 : 'I',4 : 'IV',5 : 'V',9 : 'IX',10 : 'X',40 : 'XL',50 : 'L',90 : 'XC',100 : 'C',400 : 'CD',500 : 'D',900 : 'CM',1000 : 'M'}a = int(a)if base == 1000:return a * dict_num_rom[1000]else:if 1 <= a < 4:return a * dict_num_rom[base]elif a == 4:return dict_num_rom[a*base]elif 5 <= a < 9:return dict_num_rom[5*base] + (a-5)* dict_num_rom[base]elif a == 9:return dict_num_rom[a*base]else:return ''result = ''base = 10 ** len(str(num))while num > 0:temp = num // basenum = num - temp * baseresult += num_rom(temp, base)base /= 10return result

class Solution(object):def intToRoman(self, num):""":type num: int:rtype: str"""digits = [(1000, "M"), (900, "CM"), (500, "D"), (400, "CD"), (100, "C"), (90, "XC"), (50, "L"), (40, "XL"), (10, "X"), (9, "IX"), (5, "V"), (4, "IV"), (1, "I")]roman_digits = []# Loop through each symbol.for value, symbol in digits:# We don't want to continue looping if we're done.if num == 0: breakcount, num = divmod(num, value)# Append "count" copies of "symbol" to roman_digits.roman_digits.append(symbol * count)return "".join(roman_digits)

class Solution(object):def romanToInt(self, s):""":type s: str:rtype: int"""dict_rom_num = {'I': 1,'V': 5,'X': 10,'L': 50,'C': 100,'D': 500,'M': 1000}k = 0result = 0while k < len(s)-1:if dict_rom_num[s[k]] >= dict_rom_num[s[k + 1]]:result += dict_rom_num[s[k]]k += 1else:result += dict_rom_num[s[k + 1]] - dict_rom_num[s[k]]k += 2if k < len(s):result += dict_rom_num[s[k]]return result

class Solution(object):def romanToInt(self, s):""":type s: str:rtype: int"""dict_rom_num = {'I': 1,'V': 5,'X': 10,'L': 50,'C': 100,'D': 500,'M': 1000}k = 0result = 0while k < len(s)-1:if dict_rom_num[s[k]] >= dict_rom_num[s[k + 1]]:result += dict_rom_num[s[k]]else:result -=  dict_rom_num[s[k]]k += 1 return result + dict_rom_num[s[k]]