Soln to https://files.gitter.im/scala/scala/SPxU/blob.png

sol.scala

sealed trait PitStuff
case class Rise(start: Int, end: Int) extends PitStuff
case class Fall(start: Int, end: Int) extends PitStuff

object kek extends App {
  
  def checkMax(current: Int, rise: Option[Rise], fall: Option[Fall], list: List[Int], maxPit: Int): Int ={
  list match {
    case Nil =>
      if(rise.isDefined && fall.isDefined)
        Math.max(maxPit, Math.min(fall.get.start - fall.get.end, rise.get.end - rise.get.start))
      else
        maxPit
    case z::zs =>
      if(current > z){
        rise match {
          case None =>
            if(fall.isDefined)
              checkMax(z, rise, fall.map(_.copy(end=z)), zs, maxPit)
            else
              checkMax(z, rise, Some(Fall(current, z)), zs, maxPit)
          case Some(r) =>
            if(fall.isDefined)
              checkMax(z, None, Some(Fall(current, z)), zs, Math.max(maxPit, Math.min(fall.get.start - fall.get.end, r.end - r.start)))
            else
              checkMax(z, None, Some(Fall(current, z)), zs, Math.max(maxPit, Math.min(fall.get.start - fall.get.end, rise.get.end - rise.get.start)))
        }
      } else if (current < z){
        fall match {
          case None =>
            checkMax(z, None, None, zs, maxPit)
          case Some(f) =>
            if(rise.isDefined)
              checkMax(z,rise.map(_.copy(end=z)),fall,zs,maxPit)
            else
              checkMax(z,Some(Rise(current,z)),fall,zs,maxPit)
        }
      }
      else {
        if(rise.isDefined && fall.isDefined)
          checkMax(z, None, None, zs, Math.max(maxPit, Math.min(fall.get.start - fall.get.end, rise.get.end - rise.get.start)))
        else
          checkMax(z, None, None, zs, maxPit)
      }
  }
}


def deepestPit(a: List[Int]):Int = {
  checkMax(a.head,None, None, a.tail, -1)
}


val a: List[Int] = List(0,1,3,-2,0,1,0,-4,2,7)

println(deepestPit(a))
  
  
}