1. 问题描述

给定一个整数，将其转换为罗马数字，要求返回结果的取值范围为1~3999。

2. 问题示例

4→Ⅳ，12→Ⅻ，21→XⅪ，99→XCIX。

3. 代码实现

def int_to_roman(num):
    val = [
        1000, 900, 500, 400,
        100, 90, 50, 40,
        10, 9, 5, 4,
        1
        ]
    syb = [
        "M", "CM", "D", "CD",
        "C", "XC", "L", "XL",
        "X", "IX", "V", "IV",
        "I"
        ]
    roman_num = ''
    i = 0
    while  num > 0:
        for _ in range(num // val[i]):
            roman_num += syb[i]
            num -= val[i]
        i += 1
    return roman_num
print(int_to_roman(4))  # 输出 IV
print(int_to_roman(12))  # 输出 XII
print(int_to_roman(21))  # 输出 XXI
print(int_to_roman(99))  # 输出 XCIX

def int_to_roman(num):
    roman_dict = {
        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_num = ''
    for value, symbol in roman_dict.items():
        while num >= value:
            roman_num += symbol
            num -= value
    return roman_num
print(int_to_roman(4))  # 输出 IV
print(int_to_roman(12))  # 输出 XII
print(int_to_roman(21))  # 输出 XXI
print(int_to_roman(99))  # 输出 XCIX