Day 20
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145
Day20.scala
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145
Day20.scala
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package aoc.day20
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import aoc._
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import scala.collection.mutable
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enum Pulse:
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case Low, High
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def flip = Pulse.fromOrdinal(1 - ordinal)
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import Pulse._
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sealed abstract class Module(targets: Set[String]):
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def handle(source: String, pulse: Pulse): (Module, Map[String, Pulse])
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final def broadcast(p: Pulse) = targets.toIterator.map((_, p)).toMap
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case class FlipFlop(state: Pulse, targets: Set[String]) extends Module(targets):
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def handle(source: String, pulse: Pulse) = pulse match
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case High => (this, Map.empty)
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case Low =>
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val nw = FlipFlop(state.flip, targets)
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(nw, nw.broadcast(nw.state))
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object FlipFlop:
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def apply(targets: Set[String]) = new FlipFlop(Low, targets)
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case class Conjunc(sources: Map[String, Pulse], targets: Set[String]) extends Module(targets):
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override def handle(source: String, pulse: Pulse): (Module, Map[String, Pulse]) =
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val nw = Conjunc(sources.updated(source, pulse), targets)
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(nw, nw.broadcast(if nw.sources.values.forall(_ == High) then Low else High))
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object Conjunc:
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def apply(sources: Set[String], targets: Set[String]) = new Conjunc(sources.toIterator.map((_, Low)).toMap, targets)
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case class Broadcast(targets: Set[String]) extends Module(targets):
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def handle(source: String, pulse: Pulse): (Module, Map[String, Pulse]) = (this, broadcast(pulse))
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enum ModuleTyp { case Broadcast, Flip, Conjunc }
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object Parser extends CommonParser:
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type Node = (ModuleTyp, String, Set[String])
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val name = """[a-zA-Z]+""".r
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val moduleTyp: Parser[(ModuleTyp, String)] =
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("broadcaster" ^^^ (ModuleTyp.Broadcast, "broadcaster")) | ('%' ~ name ^^ { case _ ~ name =>
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(ModuleTyp.Flip, name)
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}) |
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('&' ~ name ^^ { case _ ~ name => (ModuleTyp.Conjunc, name) })
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val node: Parser[Node] = moduleTyp ~ "->" ~ repsep(name, ",") ^^ { case (typ, name) ~ _ ~ targets =>
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(typ, name, targets.toSet)
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}
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val nodes =
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val ns = lines.map(Parser.parse(Parser.node, _).get).toSeq
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val edges = ns.flatMap((_, from, to) => to.map((from, _)))
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def sourcesOf(target: String) = edges.filter(_._2 == target).map(_._1).toSet
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ns.map: (typ, name, targets) =>
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val mod = typ match
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case ModuleTyp.Broadcast => Broadcast(targets)
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case ModuleTyp.Flip => FlipFlop(targets)
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case ModuleTyp.Conjunc => Conjunc(sourcesOf(name), targets)
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(name, mod)
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.toMap
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extension (m: Map[String, Module])
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def sendSig() = m.loop(mutable.Queue(("", "broadcaster", Low)), Seq.empty)
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def send(cache: mutable.Map[Map[String, Module], (Map[String, Module], Int, Int)]): (Map[String, Module], Int, Int) =
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cache.getOrElseUpdate(
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m, {
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val (nm, pulses) = m.sendSig()
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val (lows, highs) = pulses.partition((_, _, p) => p == Low)
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(nm, lows.size, highs.size)
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}
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)
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@scala.annotation.tailrec
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def loopUntilTwice(
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breakCond: (String, String, Pulse) => Boolean,
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first: Seq[Int] = Seq.empty,
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current: Int = 0
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): (Int, Int) =
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println(s"at $current: ${m.hashCode()}")
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first match
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case Seq(a, b) => (a, b)
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case _ =>
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val (nm, pulses) = sendSig()
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val nfirst =
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if pulses.exists(breakCond(_, _, _)) then first :+ current
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else first
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nm.loopUntilTwice(breakCond, nfirst, current + 1)
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@scala.annotation.tailrec
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private def loop(
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queue: mutable.Queue[(String, String, Pulse)],
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pulses: Seq[(String, String, Pulse)]
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): (Map[String, Module], Seq[(String, String, Pulse)]) =
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if queue.isEmpty then (m, pulses)
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else
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val (from, to, pulse) = queue.dequeue()
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val nm = m.get(to) match
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case None => m
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case Some(value) =>
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val (nmod, nexts) = m(to).handle(from, pulse)
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if to == "rs" && pulse == High then println(s"$from -> $to pulse = $pulse | $nmod")
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queue ++= nexts.toIterator.map((target, pulse) => (to, target, pulse))
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m.updated(to, nmod)
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nm.loop(queue, (from, to, pulse) +: pulses)
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// part 1
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def part1 =
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val mp = mutable.Map.empty[Map[String, Module], (Map[String, Module], Int, Int)]
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val (_, lows, highs) = (1 to 1000).foldLeft((nodes, 0, 0)):
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case ((nodes, lows, highs), _) =>
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val (pn, pl, ph) = nodes.send(mp)
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(pn, lows + pl, highs + ph)
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println(1L * lows * highs)
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def part2 =
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def sendsTo(target: String) = nodes.filter: (name, node) =>
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node match
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case Broadcast(targets) => targets.contains(target)
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case FlipFlop(_, targets) => targets.contains(target)
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case Conjunc(_, targets) => targets.contains(target)
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val v = sendsTo("rx").toSeq match // should be at most one
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case Seq((n, conj)) =>
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assert(conj.isInstanceOf[Conjunc])
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n
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case ss => throw Exception(s"Unexpected $ss")
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val toV = sendsTo(v)
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println(toV)
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// find cycles to send highs to v
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val res = toV.keys
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.map(toV => nodes.loopUntilTwice((from, to, pulse) => from == toV && to == v && pulse == High))
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.foldLeft(1L) { case (n, (a, b)) => lcm(n, b - a) }
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println(res)
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@scala.annotation.tailrec
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def gcd(a: Long, b: Long): Long = if b == 0 then a else gcd(b, a % b)
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def lcm(a: Long, b: Long) = a / gcd(a, b) * b
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@main def Day20(part: Int) = part match
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case 1 => part1
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case 2 => part2
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58
inputs/day20.input
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58
inputs/day20.input
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@ -0,0 +1,58 @@
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%qm -> mj, xn
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&mj -> hz, bt, lr, sq, qh, vq
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%qc -> qs, vg
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%ng -> vr
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%qh -> sq
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&bt -> rs
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%hh -> qs, bx
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%gk -> cs, bb
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%js -> mj
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%pc -> mj, mr
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%mb -> rd, xs
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%tp -> qs, ks
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%xq -> tp, qs
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%bx -> sz
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%mn -> cs, md
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%cv -> rd
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%rh -> rd, sv
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%md -> cs
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%pz -> mj, vq
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%bz -> rd, hk
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%jz -> vk
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%sz -> jz
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%lr -> pz, mj
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%xs -> cv, rd
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%kl -> rd, mb
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%hz -> pc
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%hk -> rz, rd
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%vk -> qc
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%bh -> zm
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%vq -> qm
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%ks -> qs, nd
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&qs -> dl, jz, bx, vk, vg, hh, sz
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&dl -> rs
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%lf -> rh, rd
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&fr -> rs
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%xn -> mj, qh
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%hf -> qs, xq
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%sv -> rd, ng
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&rs -> rx
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&rd -> ng, fr, rz, lf, vr
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%cj -> ss, cs
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broadcaster -> hh, lr, bp, lf
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%zs -> cs, mn
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%vr -> bz
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%nd -> qs
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%jb -> cj, cs
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&rv -> rs
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%bp -> cs, lx
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%ss -> zs
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%lx -> gk
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&cs -> lx, ss, rv, bh, bp
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%bb -> bh, cs
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%mf -> mj, hz
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%zm -> cs, jb
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%mr -> mj, js
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%rz -> kl
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%vg -> hf
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%sq -> mf
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