LeetCode-Unique Morse Code Words

Description：

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 “–…–.”.

Note:

The length of words will be at most 100.
Each words[i] will have length in range [1, 12].
words[i] will only consist of lowercase letters.      

Java

class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        String[] table = new String[] {".-","-...","-.-.","-..",".","..-.","--.","....","..",
                                      ".---","-.-",".-..","--","-.","---",".--.","--.-",".-.",
                                      "...","-","..-","...-",".--","-..-","-.--","--.."};
        Set<String> transformation = new HashSet<>();
        for (String word : words) {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < word.length(); i++) {
                sb.append(table[word.charAt(i) - 'a']);
            }
            if