LeetCode 804 - Unique Morse Code Words

https://leetcode.com/articles/unique-morse-code-words/

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, "cab" 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:
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 "--...--.".

    public int uniqueMorseRepresentations(String[] words) {

        String[] MORSE = new String[]{".-","-...","-.-.","-..",".","..-.","--.",

                         "....","..",".---","-.-",".-..","--","-.",

                         "---",".--.","--.-",".-.","...","-","..-",

                         "...-",".--","-..-","-.--","--.."};

        Set<String> seen = new HashSet();

        for (String word: words) {

            StringBuilder code = new StringBuilder();

            for (char c: word.toCharArray())

                code.append(MORSE[c - 'a']);

            seen.add(code.toString());

        }

        return seen.size();

    }