[LeetCode] 12. Integer to Roman 整数转为罗马数字

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

将阿拉伯整数转为罗马数字，首先要对罗马数字有了解，找到两种数字转换的规律，然后用一个Hash map来保存这些规律，然后把整数进行相应的转换。输入数字的范围(1 - 3999)。

Python:

class Solution(object):
    def intToRoman(self, num):
        """
        :type num: int
        :rtype: str
        """
        numeral_map = {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"}
        keyset, result = sorted(numeral_map.keys()), []
        
        while num > 0:
            for key in reversed(keyset):
                while num / key > 0:
                    num -= key
                    result += numeral_map[key]
                    
        return "".join(result)　　

C++:

class Solution {
public:
    string intToRoman(int num) {
        const vector<int> nums{1000, 900, 500, 400, 100, 90,
                               50, 40, 10, 9, 5, 4, 1};
        const vector<string> romans{"M", "CM", "D", "CD", "C", "XC", "L",
                                    "XL", "X", "IX", "V", "IV", "I"};

        string result;
        int i = 0;
        while (num > 0) {
            int times = num / nums[i];
            while (times--) {
                num -= nums[i];
                result.append(romans[i]);
            }
            ++i;
        }        
        return result;
    }
};

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[LeetCode] 13. Roman to Integer 罗马数字转为整数