Roman to Integer

"""
We traverse the string from right to left, keeping track of the previous numeral’s value to decide whether to add or subtract the current value.
If the current value is smaller than the previous one, we subtract it; otherwise, we add it to the total.
"""
class Solution:
    def romanToInt(self, s: str) -> int:
        dict = {'I': 1,'V': 5,'X': 10,'L': 50,'C': 100,'D': 500,'M': 1000}
        ans=0
        prev=0
        for i in reversed(s):
            cur=dict.get(i,0)
            if cur<prev and prev!=0:
                ans-=cur
            else:
                ans+=cur
            prev=cur
        return ans