[LeetCode]12. Integer to Roman解法及python代码

最新推荐文章于 2020-04-22 19:17:42 发布

原创最新推荐文章于 2020-04-22 19:17:42 发布 · 384 阅读

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本文介绍了一种将整数转换为罗马数字的算法实现，通过构建特定的映射关系和处理特殊情况，如4和9的表示，实现了从1到3999范围内整数的有效转换。

原题链接：https://leetcode.com/problems/integer-to-roman
这个题我最开始的想法很简单，由于限制输入在1~3999之间，所以可以写出1~10，10~3999间的能整除10的数的罗马数字，对于输入使用整数除法以及求余处理就可以O(1)的得到结果，下面代码：

class Solution(object):
    def intToRoman1(self, num):
        """
        :type num: int
        :rtype: str
        """
        M = ["", "M", "MM", "MMM"]
        C = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"]
        X = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"]
        I = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"]
        return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10]

接下来的代码纯粹出于个人练习，提高coding能力。因为这种题主要是规律的总结，需要在写的过程中比较细心，下面是代码，主要注意的点就是4和9的处理上：

class Solution(object):
    """
    锻炼能力的方法
    """
    def intToRoman(self, num):
        """
        :type num: int
        :rtype: str
        """
        base = ["I","II","III","IV","V","VI","VII","VIII","IX","X","L","C","D","M"]
        baseNum = 1000
        romanStr = ""
        while num > 10:
            temp = num/baseNum
            if temp !=0:
                if baseNum == 1000:
                    for i in range(temp):
                        romanStr = romanStr + base[13]
                    num = num - temp*baseNum
                    baseNum = baseNum/10
                    continue
                if baseNum == 100:
                    if temp < 4:
                        for i in range(temp):
                            romanStr =  romanStr + base[11]
                    elif temp == 4:
                        romanStr = romanStr + base[11] + base[12]
                    elif temp > 4 and temp <9:
                        romanStr = romanStr + base[12]
                        for i in range(temp-5):
                            romanStr = romanStr + base[11]
                    else:
                        romanStr = romanStr + base[11] + base[13]
                    num = num - temp*baseNum
                    baseNum = baseNum/10
                    continue
                if baseNum == 10:
                    if temp < 4:
                        for i in range(temp):
                            romanStr = romanStr + base[9]
                    elif temp == 4:
                        romanStr = romanStr + base[9] + base[10]
                    elif temp > 4 and temp <9:
                        romanStr = romanStr + base[10]
                        for i in range(temp-5):
                            romanStr = romanStr + base[9]
                    else:
                        romanStr = romanStr + base[9] + base[11]
                    num = num - temp*baseNum
                    baseNum = baseNum/10
                    continue
            else:
                baseNum = baseNum/10
        if num != 0:
            romanStr = romanStr + base[num-1]
        return romanStr