Leetcode 804. 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, "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:
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.

Code (Java):

class Solution {
    private String[] morseCodes = new String[]{
        ".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
    public int uniqueMorseRepresentations(String[] words) {
        if (words == null || words.length == 0) {
            return 0;
        }

        Set<Integer> set = new HashSet<>();
        int ans = 0;

        for (String word : words) {
            int code = getHashValue(word);
            if (!set.contains(code)) {
                ans++;
                set.add(code);
            }
        }

        return ans;
    }

    private int getHashValue(String s) {
        int ans = 0;
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            sb.append(morseCodes[s.charAt(i) - 'a']);
        }
        
        ans = morseToNumber(sb.toString());

        return ans;
    }

    private int morseToNumber(String s) {
        int ans = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            ans = ans * 2 + (c == '-' ? 1 : 0);
        }

        return ans;
    }
}