LeetCode 804: Unique Morse Code Words

Meta Data

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Difficulty: easy First Attempt: 2022-09-07

• Submissions: Accepted (first try)

Approach

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Translate each letter by the table, join into one string, and add it to a set; the answer is the set’s size (Hash Table). Letter c maps to table[ord(c) - ord("a")].

My Solution

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class Solution:
    def uniqueMorseRepresentations(self, words: List[str]) -> int:
        table = [".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---",
                 "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-",
                 "..-", "...-", ".--", "-..-", "-.--", "--.."]
        return len({"".join(table[ord(c) - ord("a")] for c in w) for w in words})

Complexity

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Time O(total characters), space O(total characters).

Mistakes to Avoid

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• Different words may share a Morse code; that is exactly what is being counted.

Interview Explanation

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I translate each word into its Morse string and return the number of distinct strings. Time is linear in the total length.