Python, a Counter one liner. Time: O(N), Space: O(N)
\nclass Solution:\n    def uncommonFromSentences(self, A: str, B: str) -> List[str]:\n        return [w for w, c in Counter(A.split() + B.split()).items() if c 
```\nclass Solution:\n    def uncommonFromSentences(self, A: str, B: str) -> List[str]:\n        return [w for w, c in Counter(A.split() + B.split()).items() if c == 1]\n```
['Python', 'Python3']