Unique Morse Code Words

Here’s a Python solution for the problem. The approach is to map each word to its Morse code representation and then count the number of unique Morse code representations using a set. This is possible because a set automatically eliminates duplicate entries. Here is the code:

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class Solution:
    def uniqueMorseRepresentations(self, words: List[str]) -> int:
        morse_codes = [".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]
        unique_representations = set()

        for word in words:
            morse_word = ""
            for char in word:
                # ord(char) - ord('a') maps 'a' to 0, 'b' to 1, and so on.
                morse_word += morse_codes[ord(char) - ord('a')]
            unique_representations.add(morse_word)

        return len(unique_representations)

Here’s what’s happening in this code:

  1. Initialize morse_codes as an array of Morse code representations for ‘a’ through ‘z’.
  2. Create an empty set unique_representations to store the unique Morse code transformations.
  3. Loop over each word in the input words.
  4. For each word, calculate the Morse code transformation by looping over each character in the word and appending the corresponding Morse code to morse_word.
  5. Add morse_word to unique_representations. If morse_word is already in unique_representations, nothing happens because sets do not allow duplicates.
  6. After looping over all words, return the number of elements in unique_representations, which represents the number of unique Morse code transformations.

Identifying Problem Isomorphism

“Jewels and Stones” has an approximate isomorphism to “Unique Morse Code Words”.

In “Jewels and Stones”, you’re given strings jewels representing the types of stones that are jewels, and stones representing the stones you have. Each character in stones is a type of stone you have, and you need to find out how many of your stones are also jewels. The letters in jewels are guaranteed distinct.

In “Unique Morse Code Words”, you’re given a list of words, and each word can be written as a concatenation of the Morse code of each letter. The Morse code of each letter is standard, similar to how each jewel type is distinct in “Jewels and Stones”. You need to find out how many different transformations result from the list of words.

Both problems involve a mapping from one set of characters to another and determining the uniqueness or frequency of occurrence in the target set based on the source set.

“Unique Morse Code Words” is more complex because it requires both the transformation of words to Morse code and the counting of unique Morse code words. On the other hand, “Jewels and Stones” primarily focuses on counting the occurrence of distinct characters (jewels) in a given string (stones).

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def uniqueMorseRepresentations(words):
    morse_code = [".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.."]
    gen_codes = set()

    for word in words:
        code = ""
        for ch in word:
            code += morse_code[ord(ch) - ord('a')]
        gen_codes.add(code)

    return len(gen_codes)

Problem Classification

The domain of this problem is related to encoding, decoding, and string manipulation. It is primarily based on the concepts of mapping, set operations and string transformations.

‘What’ Components:

  1. We have an international Morse Code encoding where each English alphabet letter maps to a series of dots and dashes.
  2. We are given an array of words where each word can be converted into Morse Code.
  3. We need to count the number of different transformations among all words we have.

This is a string transformation and counting problem. We need to transform each word into its Morse Code representation and then count the unique representations. This problem mainly revolves around the concepts of string manipulation, mapping, and set operations.

The problem is about encoding the strings into their Morse code representations and keeping track of unique transformations. The task is to find the number of unique Morse code words. This involves string manipulation (to convert each character to Morse code and concatenating them) and using a set to track the unique Morse code words. The ‘set’ data structure is used here because it inherently avoids duplication and helps count unique items. The challenge here is to correctly implement the encoding and utilize the properties of the ‘set’ data structure efficiently.

Language Agnostic Coding Drills

  1. Dissect the code and identify each distinct concept it contains:

a) Variable initialization: This includes initializing a list with Morse codes and an empty set to keep track of the generated codes.

b) Loops: There are two nested loops; the outer loop traverses the input list of words, while the inner loop traverses each character of a word.

c) String manipulation: This includes using the ‘ord’ function to convert a character to an ASCII integer, subtracting it with the ASCII value of ‘a’ to get the index of Morse code, and performing string concatenation.

d) Set operations: Adding elements to a set and using the property of a set where duplicate elements are not allowed.

e) Returning the length of a set: This gives the count of unique Morse code words.

  1. List the coding concepts or drills in order of increasing difficulty:

a) Variable initialization - Beginner: This is basic to any programming language.

b) Loops - Beginner to Intermediate: Loops are foundational, but nested loops can introduce complexity.

c) String manipulation - Intermediate: This includes understanding ASCII values and their conversion which can be a little tricky for beginners.

d) Set operations - Intermediate: Understanding the properties of set and its usage is needed.

e) Returning the length of a set - Intermediate: This is straightforward once one understands the concepts of data structures and built-in functions.

  1. Describe the problem-solving approach:

a) Begin by initializing a list with the Morse codes and an empty set for storing the generated Morse codes.

b) For each word in the list of words, calculate its Morse code representation. This is achieved by converting each character into its ASCII value, mapping it to the Morse code list, and concatenating all Morse codes for a word.

c) Add each generated Morse code of a word to the set. If a Morse code already exists in the set, it won’t be added again because sets do not allow duplicate elements.

d) After all words have been processed, return the size of the set which gives us the number of unique Morse code transformations.

In this process, each drill contributes to the final solution. The concepts of variable initialization and loops help us traverse the input and process each word. String manipulation allows us to convert each character into Morse code. Set operations help us in tracking unique Morse codes, and finally, returning the size of the set gives us the desired output.

Targeted Drills in Python

Let’s break down the uniqueMorseRepresentations problem into individual drills, ensuring each one captures a particular concept. Remember that these drills should be accessible even to Python beginners.

Drill 1: Working with lists

Description: Understanding how to define a list, access elements, and iterate over the list is fundamental in Python. Code:

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letters = ['a', 'b', 'c']
print(letters[0])  # Accessing elements
for letter in letters:  # Iterating over the list
    print(letter)

Drill 2: Using sets and its operations

Description: Sets are important for storing unique elements. They support operations like add (for adding elements) and len (to get the number of elements). Code:

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unique_elements = set()
unique_elements.add('a')
unique_elements.add('b')
unique_elements.add('a')  # Trying to add 'a' again
print(len(unique_elements))  # Should print 2 because 'a' is not added again

Drill 3: Using loops

Description: Understanding how to use a for loop to iterate over elements is crucial in most programming tasks. Code:

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for i in range(5):
    print(i)

Drill 4: Working with strings and character manipulation

Description: Being able to manipulate strings, iterate over them, and understanding character encoding are important in many text manipulation tasks. Code:

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s = 'hello'
for character in s:
    print(character)
print(ord('a'))  # Prints ASCII value of 'a'
print(chr(97))  # Prints character corresponding to ASCII value 97, which is 'a'

Problem-specific Drill: Mapping letters to Morse code

Description: In our problem, we need to map each letter to its corresponding Morse code. Here’s a simplified version of that: Code:

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morse_code_map = {'a': '.-', 'b': '-...', 'c': '-.-.'}  # A simplified map
word = 'abc'
morse_word = ''
for letter in word:
    morse_word += morse_code_map[letter]
print(morse_word)

Integrating the drills:

  1. We start by defining our Morse code map (drill 4).
  2. We then iterate over the words list (drill 1 and 3).
  3. For each word, we transform the word into Morse code (drill 4).
  4. We add this Morse code to our set (drill 2).
  5. Finally, we return the number of unique Morse code words, which is the length of our set (drill 2).