13. Roman to Integer

Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.

Python 3 Code (By Wake Liu):

class Solution:
    def romanToInt(self, s):
        """
        :type s: str
        :rtype: int
        """
        roman = {'M': 1000,'D': 500 ,'C': 100,'L': 50,'X': 10,'V': 5,'I': 1}
        ans = roman[s[-1]]
        for i in range(len(s)-1):
            ans += roman[s[i]]*((roman[s[i]]>=roman[s[i+1]])*2-1)
        return ans

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