13. Roman to Integer

https://leetcode.com/problems/roman-to-integer/

Python

class Solution:
    def romanToInt(self, s: str) -> int:
        mapper = {
            "I": 1, "V": 5, "X": 10,
            "L": 50, "C": 100, "D": 500,
            "M": 1000,
        }

        if len(s) == 1:
            return mapper[s]

        symbols = list(s)
        ans, i = 0, len(s)-1
        while i >= 0:
            cur = mapper[symbols[i]]
            j = i-1
            while mapper[symbols[j]] < mapper[symbols[i]] and j >= 0:
                cur -= mapper[symbols[j]]
                j -= 1

            ans += cur
            i = j
        return ans