13 - Roman to Integer - LeetCode

main.py

class Solution:
    def romanToInt(self, s: str) -> int:
        def value(r):
            if (r == 'I'):
                return 1
            if (r == 'V'):
                return 5
            if (r == 'X'):
                return 10
            if (r == 'L'):
                return 50
            if (r == 'C'):
                return 100
            if (r == 'D'):
                return 500
            if (r == 'M'):
                return 1000
            return -1
        
        res = 0
        i = 0
        while(i < len(s)):
            s1 = value(s[i])
            
            if(i + 1 < len(s)):
                s2 = value(s[i+1])
                
                if(s1 >= s2):
                    res = res + s1
                    i = i + 1
                else:
                    res = res + s2 - s1
                    i = i + 2
            else:
                res = res + s1
                i = i + 1
        return res