13. Roman to Integer

class Solution:
    def romanToInt(self, s: str) -> int:
        d = {
            "I": 1,
            "V": 5,
            "X": 10,
            "L": 50,
            "C": 100,
            "D": 500,
            "M": 1000,
        }
 
        ans = 0
        prev = None
        for c in s:
            ans += d[c]
            if prev and d[c] > d[prev]:
                ans -= 2 * d[prev]
            prev = c
 
        return ans
        

• make a hashmap to map the characters to their numerical values.
• just keep adding the values in the string, unless it’s in reverse order in which case we subtract.

Categories:: hashmap, string