Contents

import scala.annotation.tailrec

// Algorithm from - http://fldit-www.cs.uni-dortmund.de/~peter/PS07/HR.pdf
object PrimeFactors {
  def factors(n: Long): List[Long] = {
    assert(n >= 1, "Argument must be positive")

    @tailrec
    def primeAcc(n: Long, xs: List[Long]): List[Long] = {
      if (n == 1) xs
      else {
        val p = ld(n)
        primeAcc(n / p, p :: xs)
      }
    }

    primeAcc(n, List()).reverse
  }

  private def ld(n: Long) = ldf(2, n)

  @tailrec
  private def ldf(k: Long, n: Long): Long =
    if (n % k == 0) k
    else if (k * k > n) n
    else ldf(k + 1, n)
}

Version data entries

176 entries across 176 versions & 1 rubygems

Version	Path
trackler-2.2.1.180	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.179	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.178	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.177	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.176	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.175	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.174	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.173	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.172	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.171	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.170	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.169	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.167	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.166	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.165	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.164	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.163	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.162	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.161	tracks/scala/exercises/prime-factors/example.scala
trackler-2.2.1.160	tracks/scala/exercises/prime-factors/example.scala