2018-09-22 14:03:18 +0000   |     algorithm leetcode string   |   Viewed times   |    

题目

International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: a maps to .-, bmaps 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 "--...--.".

Note:

ArrayHashSet

用一个String[26]做一个摩斯密码词典,翻译的时候查表。翻译出来的单词用HashSet去重,并计算最终HashSet的长度。

代码

class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        Set<String> morseSet = new HashSet<>();
        for (String word : words) {
            morseSet.add(toMorse(word));
        }
        return morseSet.size();
    }
    private final String[] MORSE = new String[]{
        ".-","-...","-.-.","-..",".","..-.","--.","....","..",
        ".---","-.-",".-..","--","-.","---",".--.","--.-",".-.",
        "...","-","..-","...-",".--","-..-","-.--","--.."
    };
    private String toMorse(String word) {
        char[] arr = word.toCharArray();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < arr.length; i++) {
            sb.append(MORSE[arr[i] - 'a']);
        }
        return sb.toString();
    }
}

结果

unique-morse-code-words-1