13. Roman to Integer leetcode Python 2016 new Season

原创于 2016-01-05 20:47:34 发布 · 339 阅读

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本文介绍了一种将罗马数字转换为整数的算法实现，该算法通过一次遍历输入字符串来完成转换，并确保了时间和空间复杂度的有效控制。

Given a roman numeral, convert it to an integer.

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

O(n) time go through the whole string. O(1) space.

class Solution(object):
    def romanToInt(self, s):
        """
        :type s: str
        :rtype: int
        """
        ROMAN_HASH = {
            'M' : 1000,
            'D' : 500,
            'C' : 100,
            'L' : 50,
            'X' : 10,
            'V' : 5,
            'I' : 1
            }
        total_value = 0
        previous_value = 0
        for char in s:
            current_value = ROMAN_HASH[char]
            if previous_value < current_value:
                total_value += current_value - 2 * previous_value
            else:
                total_value += current_value
            previous_value = current_value
        return total_value