unique-morse-code-words.py

# Time:  O(n), n is the sume of all word lengths
# Space: O(n)

# 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.

class Solution(object):
    def uniqueMorseRepresentations(self, words):
        """
        :type words: List[str]
        :rtype: int
        """
        MORSE = [".-", "-...", "-.-.", "-..", ".", "..-.", "--.",
                 "....", "..", ".---", "-.-", ".-..", "--", "-.",
                 "---", ".--.", "--.-", ".-.", "...", "-", "..-",
                 "...-", ".--", "-..-", "-.--", "--.."]

        lookup = {"".join(MORSE[ord(c) - ord('a')] for c in word) \
                  for word in words}
        return len(lookup)