LeetCode 804. Unique Morse Code Words

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本文介绍了一种使用国际摩尔斯电码将英文单词转换为点和划的方法，并通过实例展示了如何计算一组单词转换后的不同摩尔斯电码表示的数量。通过遍历单词列表，将每个字母映射到其对应的摩尔斯电码，最终统计不重复的摩尔斯电码组合总数。

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.

class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        String[] morseCodes = new String[] {".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        Set<String> resultMorseCodes = new HashSet<>();        
        for(String word:words) {
            String resultCode = "";
            for(char letter:word.toCharArray()) {
                resultCode+=morseCodes[letter-'a'];
            }
            resultMorseCodes.add(resultCode);
        }
        return resultMorseCodes.size();
    }
}