884 Uncommon Words from Two Sentences

Since we are to find uncommon words - words that appear in both the sentences only once. We can use a frequency counter to keep track of the frequencies of words of both sentences, and return the ones that have a frequency of 1.

Code

Python3

def uncommonFromSentences(self, s1: str, s2: str) -> List[str]:
    
    freq = defaultdict(int)
 
    for word in (s1 + ' ' + s2).split(' '):
        if word in freq:
            freq[word] += 1
        else:
            freq[word] = 1
    
    return [word for word, count in freq.items() if count == 1]

Big O Analysis

• Runtime

  The runtime complexity here is $O(N+M)$ where N is length of string s1 and M is length of string s2.

• Memory

  The memory usage is $O(N)$ since we use the collections.defaultdict object to store the frequencies.

— A

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