Task 1

Sequences.scala

object Sequences {
  def filterPrimeCount(toFilter: Seq[Int], toCheckPrimeCount: Seq[Int]): Seq[Int] = {
    
    def isPrime(num: Int): Boolean = {
      require(num >= 0)
      num match {
        case n if n == 2 || n == 3 => true
        case n if n < 2 || n % 2 == 0 => false
        case _ => 5.to(math.sqrt(num).toInt, 2).forall(num % _ != 0)
      }
    }

    val numberIsPrimeMap: Map[Int, Boolean] = toCheckPrimeCount
      .groupBy(identity)
      .map { case (num, grouped) => (num, isPrime(grouped.length)) }
    
    toFilter.filter(n => !numberIsPrimeMap.getOrElse(n, false))
  }
}