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 "--...--.".

加班之余水个题~  利用一下set的唯一性，效率还挺高

class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        if (words == null)
            return 0;
        String[] codes = new String[]{".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        int len = words.length;
        Set<String> set = new HashSet<>();
        for (int i=0; i<len; i++) {
            String word = words[i];
            StringBuilder codeBuilder = new StringBuilder();
            for (int j=0; j<word.length(); j++) {
                codeBuilder.append(codes[word.charAt(j)-'a']);
            }
            set.add(codeBuilder.toString());
        }
        return set.size();
    }
}