Largest Odd Number in String — Python

# Time:  O(n)
# Space: O(1)

class Solution(object):
    def largestOddNumber(self, num):
        """
        :type num: str
        :rtype: str
        """
        for i in reversed(xrange(len(num))):
            if int(num[i])%2:
                return num[:i+1]
        return ""