Unique Morse Code Words, by LeetCode

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Problem tonight is this one: https://leetcode.com/problems/unique-morse-code-words/description/

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 "--...--.".

Relatively simple: parse the words, parse the letters, build the "key" based on the code, check against a hash table, store it, return the count in the hash table. Code is below, hugs & hugs!! Marcelo

public class Solution
{
public int UniqueMorseRepresentations(string[] words)
{
string[] code = { ".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.." };
Hashtable ht = new Hashtable();
foreach (string w in words)
{
string key = "";
foreach (char c in w)
{
key += code[c - 'a'].ToString();
}
if (!ht.ContainsKey(key)) ht.Add(key, true);
}
return ht.Count;
}
}

Comments

  1. TarasMarch 28, 2018 at 11:08 PM

    Very clean solution, Marcelo! Python solution:

    class Solution:
    def uniqueMorseRepresentations(self, words):
    """
    :type words: List[str]
    :rtype: int
    """
    codes = [".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]
    return len(set(["".join([codes[ord(letter) - ord("a")] for letter in word]) for word in words]))

    Or a more readable version:

    class Solution:
    def uniqueMorseRepresentations(self, words):
    """
    :type words: List[str]
    :rtype: int
    """
    codes = [".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]
    encodeLetter = lambda letter: codes[ord(letter) - ord("a")]
    encodeWord = lambda word: "".join(map(encodeLetter, word))
    return len(set(map(encodeWord, words)))

    Cheers,
    Taras

    ReplyDelete

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