Q804 Unique Morse Code Words

Unique Morse Code Words

Question

International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: "a" maps to ".-", "b" maps to "-...", "c" maps to "-.-.", and so on.

For convenience, the full table for the 26 letters of the English alphabet is given below:

[".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]

Now, given a list of words, each word can be written as a concatenation of the Morse code of each letter. For example, "cba" can be written as "-.-..--...", (which is the concatenation "-.-." + "-..." + ".-"). We'll call such a concatenation, the transformation of a word.

Return the number of different transformations among all words we have.

Example 1: Input: words = ["gin", "zen", "gig", "msg"] Output: 2 Explanation: The transformation of each word is: "gin" -> "--...-." "zen" -> "--...-." "gig" -> "--...--." "msg" -> "--...--."

There are 2 different transformations, "--...-." and "--...--.".

Approach 1: Hash Set

Intuition and Algorithm

We can transform each word into it's Morse Code representation.

After, we put all transformations into a set seen, and return the size of the set.

class Solution(object):
    def uniqueMorseRepresentations(self, words):
        MORSE = [".-","-...","-.-.","-..",".","..-.","--.",
                 "....","..",".---","-.-",".-..","--","-.",
                 "---",".--.","--.-",".-.","...","-","..-",
                 "...-",".--","-..-","-.--","--.."]

        seen = {"".join(MORSE[ord(c) - ord('a')] for c in word)
                for word in words}

        return len(seen)



def main():
    Ain=["gin", "zen", "gig", "msg"]
    solution=Solution().uniqueMorseRepresentations(Ain)
    print(solution)


if __name__ == "__main__":
    main()

Complexity Analysis

• Time Complexity: O(S), where S is the sum of the lengths of words in words. We iterate through each character of each word in words.
• Space Complexity: O(S).
• Runtime: 20 ms, faster than 95.59% of Python online submissions for Unique Morse Code Words.
• Memory Usage: 11.8 MB, less than 46.42% of Python online submissions for Unique Morse Code Words.