Unique Morse Code Words

The problem requires transforming words into Morse code and counting the number of unique transformations. By iterating through the list and using a hash table, you can track the unique codes efficiently. This pattern of array scanning combined with hash lookups is both time-efficient and space-efficient, ensuring the solution handles the input size within the problem's constraints.

Problem Statement

In this problem, you are given an array of words where each word consists of lowercase English letters. Each letter can be translated into a Morse code representation, which is a series of dots and dashes. The task is to determine how many unique Morse code transformations can be generated from the given words.

Each word in the array can be transformed into Morse code by concatenating the Morse code of each individual letter. For instance, the word 'gin' transforms into the Morse code sequence '--...-.' and 'zen' transforms into '--...-.'. The goal is to count how many distinct Morse code sequences are present among the input words.

Examples

Example 1

Input: See original problem statement.

Output: See original problem statement.

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

Example 2

Input: words = ["gin","zen","gig","msg"]

Output: 2

The transformation of each word is: "gin" -> "--...-." "zen" -> "--...-." "gig" -> "--...--." "msg" -> "--...--." There are 2 different transformations: "--...-." and "--...--.".

Example 3

Input: words = ["a"]

Output: 1

Example details omitted.

Constraints

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

Solution Approach

Array Scanning and Morse Code Transformation

For each word in the input list, iterate through its characters, convert each character to its corresponding Morse code using a predefined mapping, and concatenate the results. This gives the Morse code transformation for each word.

Hash Table for Tracking Unique Transformations

Once the Morse code transformation for each word is generated, store these transformations in a hash table (set). By using a set, only unique transformations are stored, and any duplicate transformations are automatically discarded.

Return the Count of Unique Transformations

After processing all the words, the number of unique Morse code transformations is simply the size of the set. This is the required output.

Complexity Analysis

Metric	Value
Time	O(S)
Space	O(S)

The time complexity is O(S), where S is the total number of characters across all words. This is because we scan each word and each letter inside it to generate the Morse code transformation. The space complexity is O(S) as well, due to the space used by the set to store unique Morse code transformations.

What Interviewers Usually Probe

• The candidate demonstrates the ability to handle string transformation problems using efficient data structures.
• The candidate shows awareness of array scanning and hash lookup strategies in solving similar problems.
• The candidate implements a solution that correctly tracks and counts unique transformations without unnecessary complexity.

Common Pitfalls or Variants

Common pitfalls

• Failing to correctly handle duplicate Morse code transformations, leading to an incorrect count of unique transformations.
• Not using a hash table (set) to efficiently track unique transformations, resulting in unnecessary complexity or incorrect results.
• Misunderstanding the Morse code mapping and incorrectly transforming the words into Morse code.

Follow-up variants

• Modify the problem to handle case-sensitive letters and analyze its impact on the solution.
• Alter the problem to account for a larger input size and assess if optimizations are necessary.
• Consider optimizing the solution further if the input contains many duplicate words.

FAQ

What is the time complexity of the solution for Unique Morse Code Words?

The time complexity is O(S), where S is the total number of characters across all words, as we scan each word and character once.

What data structure is most suitable for tracking unique Morse code transformations?

A hash table, or more specifically a set, is ideal for tracking unique Morse code transformations, as it automatically handles duplicates.

How does the pattern of array scanning and hash lookup apply to this problem?

This problem involves scanning each word and transforming each character into Morse code, followed by storing the transformations in a hash table to track uniqueness.

How do we handle duplicate Morse code transformations in the solution?

By using a set, duplicates are automatically ignored, and only unique Morse code transformations are kept.

What are some common mistakes when solving the Unique Morse Code Words problem?

Common mistakes include incorrectly transforming letters into Morse code, not using a hash table to track unique transformations, and failing to account for duplicate transformations.