leetcode: 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.

class Solution():
    def romanToInt(self, x):
        roman = {"I":1, "V":5, "X":10, "L":50, "C":100, "D":500, "M":1000}
        sum = 0
        for i in range(len(x) - 1):
            sum += roman[x[i]] if roman[x[i]] >= roman[x[i+1]] else -roman[x[i]]
        return sum + roman[x[-1]]


if __name__ == "__main__":
    assert Solution().romanToInt("IIVX") == 5
    assert Solution().romanToInt("MMMCMXCIX") == 3999