Q884 Uncommon Words from Two Sentences

Uncommon Words from Two Sentences

Question

We are given two sentences A and B. (A sentence is a string of space separated words. Each word consists only of lowercase letters.)

A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence.

Return a list of all uncommon words.

You may return the list in any order.

Example 1: Input: A = "this apple is sweet", B = "this apple is sour" Output: ["sweet","sour"]

Example 2: Input: A = "apple apple", B = "banana" Output: ["banana"]

Note:

1. 0 <= A.length <= 200
2. 0 <= B.length <= 200
3. A and B both contain only spaces and lowercase letters.

Approach 1: Counting

Intuition and Algorithm

Every uncommon word occurs exactly once in total. We can count the number of occurrences of every word, then return ones that occur exactly once.

class Solution:
    def uncommonFromSentences(self, A, B):
        count = {}
        for i in A.split():
            count[i] = count.get(i, 0) + 1
            # .get(i,0)意思是如果i在count里不存在，返回默认为0
        for i in B.split():
            count[i] = count.get(i, 0) + 1

        #Alternatively:
        #count = collections.Counter(A.split())
        #count += collections.Counter(B.split())

        return [word for word in count if count[word] == 1]


def main():
    A = "this apple is sweet"
    B = "this apple is sour"
    answer=Solution()
    results=answer.uncommonFromSentences(A,B)
    print(results)


if __name__ == "__main__":
    main()

• Runtime: 32 ms, faster than 99.14% of Python3 online submissions for Uncommon Words from Two Sentences.
• Memory Usage: 13.3 MB, less than 23.76% of Python3 online submissions for Uncommon Words from Two Sentences.

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Approach 2: Counting (Original)

Intuition and Algorithm

Every uncommon word occurs exactly once in total. We can count the number of occurrences of every word, then return ones that occur exactly once.

class Solution:
    def uncommonFromSentences(self, A: str, B: str) -> List[str]:
        count = {}
        for i in A.split()+B.split():
            count[i] = count.get(i, 0) + 1
        return [i for i in count if count[i] == 1]

• Runtime: 36 ms, faster than 92.30% of Python3 online submissions for Uncommon Words from Two Sentences.

• Memory Usage: 13.1 MB, less than 75.47% of Python3 online submissions for Uncommon Words from Two Sentences.