[LeetCode] Unique Morse Code Words 獨特的摩斯碼單詞

 

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 "--...--.".

 

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.

 

這道題說的就是大名鼎鼎的摩斯碼了，給了我們所有字母的摩斯碼的寫法，然后給了我們一個單詞數組，問我們表示這些單詞的摩斯碼有多少種。因為某些單詞的摩斯碼表示是相同的，比如gin和zen就是相同的。最簡單直接的方法就是我們求出每一個單詞的摩斯碼，然后將其放入一個HashSet中，利用其去重復的特性，從而實現題目的要求，最終HashSet中元素的個數即為所求，參見代碼如下：

 

class Solution {
public:
    int uniqueMorseRepresentations(vector<string>& words) {
        vector<string> morse{".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        unordered_set<string> s;
        for (string word : words) {
            string t = "";
            for (char c : word) t += morse[c - 'a'];
            s.insert(t);
        }
        return s.size();
    }
};

 

討論：這道題其實沒有充分發揮其潛力，摩斯碼的場景很好，只是作為一道Easy題未免有些可惜了。一個比較顯而易見的follow up就是，給我們一個摩斯碼，問其有幾種可能的單詞組，比如給我們一個"--...-."，那么我們知道至少有兩種zen和gin，可能還有更多，這樣是不是就更加有趣了呢？

 

類似題目：

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

https://leetcode.com/problems/unique-morse-code-words/discuss/120675/C++JavaPython-Easy-and-Concise-Solution

 

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