Roman to Integer

c++

class Solution {
public:
int romanToInt(string s) {
if (s.empty()) return 0;
unordered_map<char, int> dict = { { 'I' , 1 },{ 'V' , 5 },
{ 'X' , 10 },{ 'L' , 50 },{ 'C' , 100 },{ 'D' , 500 },{ 'M' , 1000 } };
int cum = dict[s.back()];
for (int i = s.size() - 2; i >= 0; --i) {
if (dict[s[i]] < dict[s[i + 1]])
cum -= dict[s[i]];
else
cum += dict[s[i]];
}
return cum;
}
};

python

class Solution(object):
def romanToInt(self, s):
"""
:type s: str
:rtype: int
"""
if not s: return 0
dict = {'M':1000, 'D':500, 'C':100, 'L':50, 'X':10, 'V':5, 'I':1}
s = list(s)
cum = dict[s[-1]]
for i in xrange(len(s)-2,-1,-1):
if dict[s[i]] < dict[s[i+1]]:
cum -= dict[s[i]]
else:
cum += dict[s[i]]

return cum