scalaVersion.scala

def hiddenMsg(kmer: Int, msg: String) = {
    msg.sliding(kmer).foldLeft[Map[String, Int]](Map.empty) { case (acc, curr) =>
      if (acc.isDefinedAt(curr)) acc.updated(curr, acc(curr) + 1)
      else acc.updated(curr, 1)
    }
  }