Leetcode13. Roman to Integer

题目描述：

Given a roman numeral, convert it to an integer.

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

罗马数字转换为阿拉伯数字的注意点有这么几点：

1.  对应意义'I':1, 'V':5, 'X':10, 'L':50, 'C':100, 'D':500, 'M':1000

2.  左大于等于右简单加法，左小于右简单减法，优先级从我的理解来看是减法大于加法。

python

class Solution(object):
    def romanToInt(self, s):
        """
        :type s: str
        :rtype: int
        """
        dict = {'I':1, 'V':5, 'X':10, 'L':50, 'C':100, 'D':500, 'M':1000}
        if s =='0':
            return false
        else:
            res = 0
            for i in range(len(s)):
                if i == 0 or dict[s[i]] <= dict[s[i-1]]:
                    res += dict[s[i]]
                else:
                    res += dict[s[i]] - 2*dict[s[i-1]]
        if res in range(1,4000):
            return res
        else:
            return false