function uniqueWords(text: string): string[] {
  if (!text.trim()) return [];
  let freq: Record<string, number> = {}
  let words = text.toLowerCase().split(' ')
  words.forEach((word) => freq[word] = (freq[word] || 0) + 1)
  return words.filter((word) => freq[word] === 1 )
}

// Do not modify: needed to evaluate the result.
export { uniqueWords };