Day17.scala

case class TargetArea(x1:Int, x2:Int, y1:Int, y2:Int)

val targetArea = TargetArea(124,174,-123,-86) //TargetArea(20, 30, -10, -5)

case class Probe(x:Int, y:Int, maxY:Int)
case class Velocity(x:Int, y:Int)

def nextPosition(p: Probe, v: Velocity) : (Probe, Velocity) = {
  val nvx = nextXV(v.x)
  val nvy = nextYV(v.y)

//  println("next p ..." + (p.x + v.x) + " ... " + (p.y + v.y))
//  println("next velo ..." + nvx + " ... " + nvy)
  val maxy = math.max(p.maxY, p.y + v.y)

  (Probe(p.x + v.x, p.y + v.y, maxy), Velocity(nvx, nvy))
}

def nextXV(x:Int):Int = {
  if ( x >= 1) x - 1
  else if ( x <= -1) x + 1
  else 0
}

def nextYV(y:Int):Int = {
  y - 1
}

def findY(p:Probe, v: Velocity): Option[(Int,Int)] = {
  val next = nextPosition(p, v)

  if (next._1.x > targetArea.x2 || next._1.y < targetArea.y1) None
  else if ( next._1.x >= targetArea.x1 && next._1.x <= targetArea.x2 &&
      next._1.y >= targetArea.y1 && next._1.y <= targetArea.y2
  ) Some(next._1.y, next._1.maxY)
  else findY(next._1, next._2)
}

object Main extends App {
  val q =
    for (
      x <- 0 to targetArea.x2;
      y <- targetArea.y1 to -targetArea.y1;
      if findY(Probe(0,0,0), Velocity(x,y)) != None
  ) yield findY(Probe(0,0,0), Velocity(x,y)).get

 val r =
      for (
        x <- 0 to targetArea.x2;
        y <- targetArea.y1 to -targetArea.y1;
        if findY(Probe(0,0,0), Velocity(x,y)) != None
 ) yield (x,y)

  val miny = q.map(_._1).min
  println("q1=" + q.filter(_._1 == miny).map(_._2).max)
  println("q2=" + r.length)
//  ymin = q.map(x -> x._1).min
//
//  println(q.max)
//
//  println(q.flatten)
//
//
//  println(findY(Probe(0,0), Velocity(7,2)))
//  println(findY(Probe(0,0), Velocity(6,3)))
//  println(findY(Probe(0,0), Velocity(9,0)))
//  println(findY(Probe(0,0,0), Velocity(6,9)))
//  println(findY(Probe(0,0), Velocity(17,-4)))
}