scalania

gistfile1.scala

  def p8[T](list: Seq[T]): Seq[T] =
    list.foldRight(Seq[T]())((e, l) =>
      if (l.isEmpty || e != l.head) e +: l
      else l)

  def p9[T](list: Seq[T]): Seq[Seq[T]] =
    list.foldRight(Seq[Seq[T]]())((e, l) =>
      if (l.isEmpty || e != l.head.head) Seq(e) +: l
      else (e +: l.head) +: l.tail)

  def p10[T](list: Seq[T]): Seq[(Int, T)] =
    p9(list).map(l => (l.length, l.head))

  def p11[T](list: Seq[T]): Seq[Either[(Int, T), T]] =
    p9(list).map { l =>
      if (l.size > 1) Left(l.length, l.head)
      else Right(l.head)
    }

  def p12[T](list: Seq[(Int, T)]): Seq[T] =
    list.flatMap { case (n, e) => Seq.fill(n)(e) }


  def p13[T](list: Seq[T]): Seq[(Int, T)] =
    list.foldRight(Seq[(Int, T)]())((e, l) => 
      if (l.isEmpty || e != l.head._2) (1, e) +: l
      else (l.head._1 + 1, l.head._2) +: l.tail)

  def p14[T](list: Seq[T]): Seq[T] = {
    @tailrec
    def go(list: Seq[T], acc: Seq[T]): Seq[T] = list match {
      case Seq() => acc
      case h :: t => go(t, h +: h +: acc)
    }
    go(list, Seq()).reverse
  }  

  def p16[T](nr: Int, list: Seq[T]): Seq[T] =
    list.zipWithIndex.filter(t => (t._2 + 1) % nr != 0).map(_._1)