class Solution:
# def romanToInt(self, s):
# """
# :type s: str
# :rtype: int
# """
# roman = {'I': 1, 'V': 5, 'X': 10,
# 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
# result = 0
# last = s[-1]
# for t in reversed(s):
# if t == 'C' and last in ['D', 'M']:
# result -= roman[t]
# elif t == 'X' and last in ['L', 'C']:
# result -= roman[t]
# elif t == 'I' and last in ['V', 'X']:
# result -= roman[t]
# else:
# result += roman[t]
# last = t
# return result
def romanToInt(self, s):
roman = {'I': 1, 'V': 5, 'X': 10,
'L': 50, 'C': 100, 'D': 500, 'M': 1000}
prev, total = 0, 0
for c in s:
curr = roman[c]
total += curr
# need to subtract
if curr > prev:
total -= 2 * prev
prev = curr
return total
