Day 16

aoc/resources/day16Input.txt

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+Valve DJ has flow rate=0; tunnels lead to valves ZH, AA
+Valve LP has flow rate=0; tunnels lead to valves AA, EE
+Valve GT has flow rate=0; tunnels lead to valves FJ, AW
+Valve RO has flow rate=5; tunnels lead to valves NO, FD, QV, BV
+Valve PS has flow rate=0; tunnels lead to valves FY, UV
+Valve QV has flow rate=0; tunnels lead to valves EB, RO
+Valve MV has flow rate=0; tunnels lead to valves FL, EB
+Valve RN has flow rate=0; tunnels lead to valves AW, LQ
+Valve HF has flow rate=0; tunnels lead to valves QN, HW
+Valve PY has flow rate=19; tunnel leads to valve SN
+Valve AT has flow rate=0; tunnels lead to valves YQ, UY
+Valve UY has flow rate=3; tunnels lead to valves KV, ID, AT, PB, PG
+Valve YI has flow rate=0; tunnels lead to valves FL, FD
+Valve EB has flow rate=8; tunnels lead to valves MV, GQ, QV
+Valve ID has flow rate=0; tunnels lead to valves NO, UY
+Valve FY has flow rate=15; tunnels lead to valves LQ, PS
+Valve GQ has flow rate=0; tunnels lead to valves EB, KM
+Valve HW has flow rate=0; tunnels lead to valves FJ, HF
+Valve CQ has flow rate=17; tunnels lead to valves KM, GO
+Valve AW has flow rate=20; tunnels lead to valves RN, GT, WH, MX
+Valve BV has flow rate=0; tunnels lead to valves RO, ZH
+Valve PB has flow rate=0; tunnels lead to valves UY, AA
+Valve MX has flow rate=0; tunnels lead to valves AW, YG
+Valve DE has flow rate=4; tunnels lead to valves MM, PZ, PG, DS, EP
+Valve AA has flow rate=0; tunnels lead to valves EP, PB, LP, JT, DJ
+Valve QN has flow rate=23; tunnels lead to valves SN, HF
+Valve GO has flow rate=0; tunnels lead to valves CQ, MK
+Valve PZ has flow rate=0; tunnels lead to valves IJ, DE
+Valve PG has flow rate=0; tunnels lead to valves UY, DE
+Valve FL has flow rate=18; tunnels lead to valves MV, YI
+Valve DS has flow rate=0; tunnels lead to valves DE, ZH
+Valve ZH has flow rate=11; tunnels lead to valves YQ, BV, DJ, DS, SB
+Valve KV has flow rate=0; tunnels lead to valves UY, IJ
+Valve UV has flow rate=9; tunnels lead to valves MM, PS, YG
+Valve WH has flow rate=0; tunnels lead to valves JT, AW
+Valve FD has flow rate=0; tunnels lead to valves YI, RO
+Valve FJ has flow rate=24; tunnels lead to valves HW, GT
+Valve JT has flow rate=0; tunnels lead to valves AA, WH
+Valve SN has flow rate=0; tunnels lead to valves PY, QN
+Valve KM has flow rate=0; tunnels lead to valves GQ, CQ
+Valve LQ has flow rate=0; tunnels lead to valves RN, FY
+Valve NO has flow rate=0; tunnels lead to valves ID, RO
+Valve SB has flow rate=0; tunnels lead to valves ZH, IJ
+Valve MK has flow rate=25; tunnel leads to valve GO
+Valve YG has flow rate=0; tunnels lead to valves MX, UV
+Valve IJ has flow rate=16; tunnels lead to valves EE, KV, PZ, SB
+Valve EP has flow rate=0; tunnels lead to valves AA, DE
+Valve MM has flow rate=0; tunnels lead to valves UV, DE
+Valve YQ has flow rate=0; tunnels lead to valves AT, ZH
+Valve EE has flow rate=0; tunnels lead to valves LP, IJ

aoc/src/Day16.scala

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+import scala.io.Source
+import scala.util.chaining.*
+import scala.collection.mutable
+
+object Day16 extends App:
+
+  val valves = Source
+    .fromURL(getClass.getResource("day16Input.txt"))
+    .mkString
+    .split('\n')
+    .map(
+      _.drop(6)
+        .replaceAllLiterally("has flow rate=", "")
+        .replaceAllLiterally("; tunnels lead to valves", "")
+        .replaceAllLiterally("; tunnel leads to valve", "")
+        .replaceAllLiterally(",", "")
+        .split(" ")
+    )
+    .map(l => Valve(l.head, l(1).toInt, l.drop(2).toList))
+
+  final case class Valve(name: String, rate: Int, tunnels: List[String])
+
+  val valvesMap     = valves.map(v => (v.name, v)).toMap
+  val workingValves = valves.filter(_.rate > 0).map(_.name).toList
+
+  val distances = mutable.Map.from(
+    for
+      valve <- valves
+      targetValves = valves.map(_.name).map((_, 9999)).to(mutable.Map)
+    yield (valve.name, targetValves)
+  )
+
+  for
+    valve  <- valves
+    tunnel <- valve.tunnels
+  do distances(valve.name)(tunnel) = 1
+
+  for
+    k <- valves.map(_.name)
+    i <- valves.map(_.name)
+    j <- valves.map(_.name)
+    current = distances(i)(j)
+    dist    = distances(i)(k) + distances(k)(j)
+    if current > dist
+  do distances(i)(j) = dist
+
+  def computeFlow(current: String, rest: List[String], timeLeft: Int): Int =
+    rest
+      .filter(distances(current)(_) < timeLeft)
+      .map(r => (r, rest.filterNot(_ == r)))
+      .map { case (r, rest) =>
+        valvesMap(r).rate * (timeLeft - distances(current)(r) - 1) +
+          computeFlow(r, rest, timeLeft - distances(current)(r) - 1)
+      }
+      .prepended(0)
+      .max
+
+  def computeFlow2(current: String, rest: List[String], timeLeft: Int): Int =
+    rest
+      .filter(distances(current)(_) < timeLeft)
+      .map(r => (r, rest.filterNot(_ == r)))
+      .map { case (r, rest) =>
+        valvesMap(r).rate * (timeLeft - distances(current)(r) - 1) +
+          computeFlow2(r, rest, timeLeft - distances(current)(r) - 1)
+      }
+      .prepended(computeFlow("AA", rest, 26))
+      .max
+
+  val part1 = computeFlow("AA", workingValves, 30)
+  println("Part 1:")
+  println(part1)
+
+  val part2 = computeFlow2("AA", workingValves, 26)
+  println("Part 2:")
+  println(part2)
+end Day16