class Solution(object):
    def uncommonFromSentences(self, s1, s2):
        """
        :type s1: str
        :type s2: str
        :rtype: List[str]
        """
        s1Set = set(s1.split(' '))
        s2Set = set(s2.split(' '))
        s1Set.symmetric_difference_update(s2Set)

        s1Common = self.getComonWords(s1)
        s2Common = self.getComonWords(s2)

        s1Set.difference_update(s1Common)
        s1Set.difference_update(s2Common)

        return s1Set

    def getComonWords(self, sentence):
        uncommon = set()
        common = set()

        for word in sentence.split(' '):
            if word in common:
                continue
            if word in uncommon:
                uncommon.remove(word)
                common.add(word)
                continue
            uncommon.add(word)

        return common