Title：Unique Morse Code Words  804

Difficulty：Easy

原題leetcode地址: https://leetcode.com/problems/unique-morse-code-words/

1.   Set集合的唯一性

時間複雜度：O(n^2)，巢狀for迴圈。

空間複雜度：O(n)，申請了Set，最長是字串陣列的長度。

    /**
     * Set集合的唯一性
     * @param words
     * @return
     */
    public static int uniqueMorseRepresentations(String[] words) {

        String sm[] = {".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        Set<String> set = new HashSet<>();

        for (String word : words) {
            StringBuilder sb = new StringBuilder();
            for (char c : word.toCharArray()) {
                sb.append(sm[c - 'a']);
            }
            set.add(sb.toString());
        }

        return set.size();

    }