804. 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:

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

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.

 

Example 1:

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 "--...--.".

Example 2:

Input: words = ["a"]
Output: 1

 

Constraints:

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

Solutions

Solution 1

Python Code
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class Solution:
    def uniqueMorseRepresentations(self, words: List[str]) -> int:
        codes = [
            ".-",
            "-...",
            "-.-.",
            "-..",
            ".",
            "..-.",
            "--.",
            "....",
            "..",
            ".---",
            "-.-",
            ".-..",
            "--",
            "-.",
            "---",
            ".--.",
            "--.-",
            ".-.",
            "...",
            "-",
            "..-",
            "...-",
            ".--",
            "-..-",
            "-.--",
            "--..",
        ]
        s = {''.join([codes[ord(c) - ord('a')] for c in word]) for word in words}
        return len(s)

Java Code
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class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        String[] codes = new String[] {".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....",
            "..", ".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-",
            "..-", "...-", ".--", "-..-", "-.--", "--.."};
        Set<String> s = new HashSet<>();
        for (String word : words) {
            StringBuilder t = new StringBuilder();
            for (char c : word.toCharArray()) {
                t.append(codes[c - 'a']);
            }
            s.add(t.toString());
        }
        return s.size();
    }
}

C++ Code
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class Solution {
public:
    int uniqueMorseRepresentations(vector<string>& words) {
        vector<string> codes = {".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-", ".-..", "--", "-.",
            "---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.."};
        unordered_set<string> s;
        for (auto& word : words) {
            string t;
            for (char& c : word) t += codes[c - 'a'];
            s.insert(t);
        }
        return s.size();
    }
};

Go Code
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func uniqueMorseRepresentations(words []string) int {
	codes := []string{".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-", ".-..", "--", "-.",
		"---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.."}
	s := make(map[string]bool)
	for _, word := range words {
		t := &strings.Builder{}
		for _, c := range word {
			t.WriteString(codes[c-'a'])
		}
		s[t.String()] = true
	}
	return len(s)
}

TypeScript Code
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const codes = [
    '.-',
    '-...',
    '-.-.',
    '-..',
    '.',
    '..-.',
    '--.',
    '....',
    '..',
    '.---',
    '-.-',
    '.-..',
    '--',
    '-.',
    '---',
    '.--.',
    '--.-',
    '.-.',
    '...',
    '-',
    '..-',
    '...-',
    '.--',
    '-..-',
    '-.--',
    '--..',
];

function uniqueMorseRepresentations(words: string[]): number {
    return new Set(
        words.map(word => {
            return word
                .split('')
                .map(c => codes[c.charCodeAt(0) - 'a'.charCodeAt(0)])
                .join('');
        }),
    ).size;
}

Rust Code
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use std::collections::HashSet;
impl Solution {
    pub fn unique_morse_representations(words: Vec<String>) -> i32 {
        const codes: [&str; 26] = [
            ".-",
            "-...",
            "-.-.",
            "-..",
            ".",
            "..-.",
            "--.",
            "....",
            "..",
            ".---",
            "-.-",
            ".-..",
            "--",
            "-.",
            "---",
            ".--.",
            "--.-",
            ".-.",
            "...",
            "-",
            "..-",
            "...-",
            ".--",
            "-..-",
            "-.--",
            "--..",
        ];
        words
            .iter()
            .map(|word| {
                word.as_bytes()
                    .iter()
                    .map(|v| codes[(v - b'a') as usize])
                    .collect::<String>()
            })
            .collect::<HashSet<String>>()
            .len() as i32
    }
}