factorize.scala

import annotation.tailrec
import collection.parallel.mutable.ParSeq

def factorize(n: Long): List[Long] = {
  @tailrec
  def factors(tuple: (Long, Long, List[Long], Int)): List[Long] = {
    tuple match {
      case (1, _, acc, _)                 => acc
      case (n, k, acc, _) if (n % k == 0) => factors((n / k, k, acc ++ ParSeq(k), Math.sqrt(n / k).toInt))
      case (n, k, acc, sqr) if (k < sqr)  => factors(n, k + 1, acc, sqr)
      case (n, k, acc, sqr) if (k >= sqr) => factors((1, k, acc ++ ParSeq(n), 0))
    }
  }
  factors((n, 2, List[Long](), Math.sqrt(n).toInt))
}

(1 to 1000) foreach { i =>
  val list = factorize(i)
  list match {
    case head :: Nil =>
      println(f"It's prime $i%09d")
    case _ =>
      println(f"Factorized $i%09d -> ${list.mkString(", ")}")
  }
}