in case be asked to implement recursive version

```
class Solution(object):
def romanToInt(self, s):
"""
:type s: str
:rtype: int
"""
roman = {'M': 1000,'D': 500 ,'C': 100,'L': 50,'X': 10,'V': 5,'I': 1}
self.res = 0
def dfs(idx, prev):
if idx > len(s) - 1:
return
curr = roman[s[idx]]
if curr > prev and idx > 0:
self.res += curr - 2 * prev
else:
self.res += curr
dfs(idx + 1, curr)
dfs(0, None)
return self.res
```