Advent of Code 2021-17.scala

import java.io.FileInputStream
import scala.annotation.tailrec
import scala.io.StdIn

case class Range(min: Int, max: Int)
case class Area(x: Range, y: Range) {
  def isInArea(point: Point): Boolean = x.min <= point.x && point.x <= x.max && y.min <= point.y && point.y <= y.max
}
case class Point(x: Int, y: Int) {
  def + (another: Point): Point = Point(x + another.x, y + another.y)
}

@tailrec
def maxYPos(yVelocity: Int, yPos: Int = 0): Int =
  if 0 >= yVelocity then
    yPos
  else
    maxYPos(yVelocity - 1, yPos + yVelocity)

def solve17_1(area: Area): Int =
  maxYPos(-area.y.min - 1)



@tailrec
def isInArea(pos: Point, velocity: Point, area: Area): Boolean =
  if pos.x > area.x.max || pos.y < area.y.min then
    false
  else if area.isInArea(pos) then
    true
  else
    isInArea(pos + velocity, Point(velocity.x - 1 max 0, velocity.y - 1), area)

def solve17_2(area: Area): Int =
  val minY = area.y.min
  val maxY = -area.y.min - 1
  val maxX = area.x.max
  val count = (1 to maxX).flatMap(x => (minY to maxY).map(y => Point(x, y))).count(isInArea(Point(0, 0), _, area))
  count



def parse(line: String): Area =
  val Array(_, values) = line.split(":")
  val Array(xs, ys) = values.trim.split(",")
  val Array(xStart, xEnd) = xs.trim.drop(2).split("\\.\\.")
  val Array(yStart, yEnd) = ys.trim.drop(2).split("\\.\\.")
  Area(Range(xStart.toInt, xEnd.toInt), Range(yStart.toInt, yEnd.toInt))

@main def solve17(): Unit =
  val in = new FileInputStream("example17-2.in")
  System.setIn(in)
  val inputs = StdIn.readLine()
  println(solve17_1(parse(inputs)))
  println(solve17_2(parse(inputs)))