Day 3

aoc/src/main/scala/aoc/y2018/Day03.scala

@@ -0,0 +1,72 @@
+package aoc.y2018
+
+import aoc.Day
+
+object Day03 extends Day {
+
+  import fastparse._, SingleLineWhitespace._
+
+  case class Claim(id: Int, pos: (Int, Int), size: (Int, Int))
+
+  def numParser[_: P]: P[Int] = P(CharIn("0-9").rep(1).!).map(_.toInt)
+  def idParser[_: P]: P[Int] = P("#" ~ numParser)
+  def coordParser[_: P]: P[(Int, Int)] = P(numParser ~ "," ~ numParser)
+  def dimensParser[_: P]: P[(Int, Int)] = P(numParser ~ "x" ~ numParser)
+  def claimParser[_: P]: P[Claim] = P(idParser ~ "@" ~ coordParser ~ ":" ~ dimensParser).map {
+    case (id, coords, dimens) => Claim(id, coords, dimens)
+  }
+  def claimsParser[_: P]: P[List[Claim]] = P(claimParser.rep(1, "\n"./)).map(_.toList)
+
+  def getClaims(input: String): List[Claim] = {
+    val Parsed.Success(claims, _) = parse(input, claimsParser(_))
+    claims
+  }
+
+  def insideRange(c: (Int, Int), p: (Int, Int), s: (Int, Int)): Boolean = {
+    (c, p, s) match {
+      case ((cx, cy), (px, py), (sw, sh)) =>
+        cx >= px &&
+        cx < px + sw &&
+        cy >= py &&
+        cy < py + sh
+    }
+  }
+
+  def mapSection[A](l: List[List[A]], p: (Int, Int), s: (Int, Int), f: A => A): List[List[A]] = {
+    val coordinated = l.zipWithIndex.map { case (n, i) => n.zipWithIndex.map { case (e, y) => (e, y, i) } }
+    val mapped = coordinated.map(_.map { case (e, y, x) => if(insideRange((x, y), p, s)) f(e) else e })
+    mapped
+  }
+
+  def maxSize(c: List[Claim]): (Int, Int) = {
+    (c.map {
+      case Claim(_, (x, _), (w, _)) => x + w
+    }.max, c.map {
+      case Claim(_, (_, y), (_, h)) => y + h
+    }.max)
+  }
+
+  override def part1(input: String): String = {
+    val claims = getClaims(input)
+    val (highestW, highestH) = maxSize(claims)
+    val starting: List[List[Int]] = List.fill(highestW)(List.fill(highestH)(0))
+    val finished = claims.foldLeft(starting)((acc, cc) => {
+      mapSection(acc, cc.pos, cc.size, (i: Int) => i + 1)
+    })
+    finished.flatten.count(_ > 1).toString
+  }
+
+  override def part2(input: String): String = {
+    val claims = getClaims(input)
+    val (highestW, highestH) = maxSize(claims)
+    val starting: List[List[List[Int]]] = List.fill(highestW)(List.fill(highestH)(List()))
+    val finished = claims.foldLeft(starting)((acc, cc) => {
+      mapSection(acc, cc.pos, cc.size, (e: List[Int]) => cc.id :: e)
+    })
+    val all = finished.flatten
+    val oneInhabitant = all.filter(_.size == 1).map(_.head).toSet
+    val solitary = oneInhabitant.filter(i => all.filter(_.contains(i)).forall(_.size == 1))
+    solitary.head.toString
+  }
+
+}

aoc/src/main/scala/aoc/y2018/package.scala

@@ -4,7 +4,8 @@ package object y2018 extends Year {
 
   override def days: Map[String, Day] = Map(
     "1" -> Day01,
-    "2" -> Day02
+    "2" -> Day02,
+    "3" -> Day03,
   )
 
 }