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Word Tokenizer and Vocabulary

Split text into lowercase words and build a vocabulary sorted by frequency, the first step of any language model.

O que você vai aprender

  • Split text into lowercase word tokens
  • Count word frequencies
  • Sort a vocabulary by frequency, then alphabetically

Problema

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Language models work with tokens, not raw text. A simple tokenizer lowercases the text and treats every run of letters a-z and digits 0-9 as a word; everything else (spaces, punctuation, other characters) separates words.

Build the vocabulary: the distinct words, sorted by how often they appear (most frequent first), with ties broken alphabetically. A word's position in this list is its token ID.

Implement build_vocabulary(text).

Input

text: Any text.

Output

Return the vocabulary as a list of words. Return an empty list if the text has no words.

Restrições

0 ≤ length of text ≤ 100,000

Exemplos

Exemplo 1
Entrada:
text = "The cat sat on the mat. The end!"

Saída esperada:
expected = ["the", "cat", "end", "mat", "on", "sat"]
Entrada:
std::string text = "The cat sat on the mat. The end!";

Saída esperada:
std::vector<std::string> expected = {"the", "cat", "end", "mat", "on", "sat"};
Entrada:
string text = "The cat sat on the mat. The end!";

Saída esperada:
string[] expected = new string[] {"the", "cat", "end", "mat", "on", "sat"};

Explicação

Lowercased, the words are the, cat, sat, on, the, mat, the, end. "the" appears 3 times; the rest appear once and are sorted alphabetically: ["the", "cat", "end", "mat", "on", "sat"].

Exemplo 2
Entrada:
text = "AI, ai and A.I. (2024)"

Saída esperada:
expected = ["ai", "2024", "a", "and", "i"]
Entrada:
std::string text = "AI, ai and A.I. (2024)";

Saída esperada:
std::vector<std::string> expected = {"ai", "2024", "a", "and", "i"};
Entrada:
string text = "AI, ai and A.I. (2024)";

Saída esperada:
string[] expected = new string[] {"ai", "2024", "a", "and", "i"};

Explicação

Words: ai, ai, and, a, i, 2024. "ai" appears twice; the others once, sorted alphabetically with digits before letters: ["ai", "2024", "a", "and", "i"].

Referências

Este desafio foi adaptado para o CodeUtility. Siga o enunciado e as restrições acima.

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