Advent of Code 2021-5.scala

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

case class Point(x: Int, y: Int)
case class Vent(p0: Point, p1: Point)

implicit class MapAdder(map: Map[Point, Int]) {
  def addValueOrInsert(key: Point, v: Int): Map[Point, Int] = {
    map.updated(key, map.getOrElse(key, 0) + 1)
  }
}

def solve5(inputs: Vector[Vent], updater: (Map[Point, Int], Point, Point) => Map[Point, Int]): Int = {
  val maps = inputs.foldLeft(Map[Point, Int]()) { (acc, vent) =>
    updater(acc, vent.p0, vent.p1)
  }
  maps.count(2 <= _._2)
}

def solve5_1Updater(acc: Map[Point, Int], p0: Point, p1: Point): Map[Point, Int] = {
  if p0.x == p1.x then
    val y0 = p0.y min p1.y
    val y1 = p0.y max p1.y
    (y0 to y1).foldLeft(acc) { (map, y) => map.addValueOrInsert(Point(p0.x, y), 1) }
  else if p0.y == p1.y then
    val x0 = p0.x min p1.x
    val x1 = p0.x max p1.x
    (x0 to x1).foldLeft(acc) { (map, x) => map.addValueOrInsert(Point(x, p0.y), 1) }
  else
    acc
}

def solve5_1(inputs: Vector[Vent]): Int = {
  solve5(inputs, solve5_1Updater)
}

def solve5_2Updater(acc: Map[Point, Int], p0: Point, p1: Point): Map[Point, Int] = {
  if p1.y - p0.y == p1.x - p0.x then
    val deltaMin = 0 min (p1.x - p0.x)
    val deltaMax = 0 max (p1.x - p0.x)
    (deltaMin to deltaMax).foldLeft(acc) { (map, delta) => map.addValueOrInsert(Point(p0.x + delta, p0.y + delta), 1) }
  else if -(p1.y - p0.y) == p1.x - p0.x then
    val deltaMin = 0 min (p1.x - p0.x)
    val deltaMax = 0 max (p1.x - p0.x)
    (deltaMin to deltaMax).foldLeft(acc) { (map, delta) => map.addValueOrInsert(Point(p0.x + delta, p0.y - delta), 1) }
  else
    solve5_1Updater(acc, p0, p1)
}

def solve5_2(inputs: Vector[Vent]): Int = {
  solve5(inputs, solve5_2Updater)
}

@main def solve5(): Unit =
  val in = new FileInputStream("example5-2.in")
  System.setIn(in)
  val inputs = Iterator.continually(StdIn.readLine())
    .takeWhile(line => null != line && line.trim.nonEmpty)
    .map(line => {
      val Array(x0, y0, _, x1, y1) = line.split("[, ]")
      Vent(Point(x0.toInt, y0.toInt), Point(x1.toInt, y1.toInt))
    })
    .toVector
  println(solve5_1(inputs)) // 5 8350
  println(solve5_2(inputs)) // 12 19374