Unique Morse Code Words

Problem

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:

[".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]

Given an array of strings words where 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 of "-.-.", ".-", and "-...". We will call such a concatenation the transformation of a word.

Return the number of different transformations among all words we have.

Constraints

• 1 <= words.length <= 100
• 1 <= words[i].length <= 12
• words[i] consists of lowercase English letters.

Solution

The problem Unique Morse Code Words can be solved using a hash set to count unique transformations.

Implementation

static const int fast_io = []()
{
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    return 0;
}();

class Solution
{
  public:
    int uniqueMorseRepresentations(vector<string> &words)
    {
        string morse_code[26] = {".-", "-...", "-.-.", "-..",  ".",   "..-.", "--.", "....", "..",   ".---", "-.-",  ".-..", "--",
                                 "-.", "---",  ".--.", "--.-", ".-.", "...",  "-",   "..-",  "...-", ".--",  "-..-", "-.--", "--.."};

        unordered_set<string> hashmap;
        for (string &word : words)
        {
            string xform = "";
            for (char &ch : word)
                xform += morse_code[ch - 'a'];
            hashmap.insert(xform);
        }

        return hashmap.size();
    }
};