Java

import java.util.HashSet;
import java.util.Set;

/**

 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 class Unique_Morse_Code_Words {
    class Solution {
        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();
        }
    }
}

Java

class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        String[] morseArray = {".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        Set<String> set = new HashSet<String>();
        for (String word : words) {
            StringBuffer sb = new StringBuffer();
            char[] array = word.toCharArray();
            for (char c : array)
                sb.append(morseArray[c - 'a']);
            set.add(sb.toString());
        }
        return set.size();
    }
}

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