Day 12

aoc/src/main/scala/aoc/y2017/Day11.scala

@@ -75,7 +75,7 @@ object Day11 extends Day {
   override def part2(input: String): String = {
     val directions = getDirections(input)
     def findFurthest(directions: List[Direction], step: Int = 1, max: Int = 0): Int = {
-      if(step > directions.length) {
+      if (step > directions.length) {
         max
       } else {
         val mds = directions.take(step)

aoc/src/main/scala/aoc/y2017/Day12.scala

@@ -0,0 +1,54 @@
+package aoc.y2017
+
+import aoc.Day
+
+import scalax.collection.Graph
+import scalax.collection.GraphPredef._, scalax.collection.GraphEdge._
+import scalax.collection.edge.Implicits._
+
+object Day12 extends Day {
+
+  import fastparse._, SingleLineWhitespace._
+
+  def channelNameParser[_: P]: P[Int] = P(CharIn("0-9").rep(1).!).map(_.toInt)
+  def connectionListParser[_: P]: P[Seq[Int]] = P(channelNameParser.rep(1, ","./))
+
+  def channelParser[_: P]: P[Seq[DiEdge[Int]]] = P(channelNameParser ~ "<->" ~ connectionListParser).map {
+    case (name, connections) => connections.map(name ~> _)
+  }
+
+  def channelsParser[_: P]: P[Graph[Int, DiEdge]] =
+    P(channelParser.rep(1, "\n"./)).map(s => {
+      val allEdges = s.flatten
+      Graph.apply(allEdges: _*)
+    })
+
+  def getGraph(input: String): Graph[Int, DiEdge] = {
+    val Parsed.Success(graph, _) = parse(input, channelsParser(_))
+    graph
+  }
+
+  def findGroup(graph: Graph[Int, DiEdge])(startingNode: graph.NodeT): Set[graph.NodeT] =
+    graph.nodes.filter(_.pathTo(startingNode).isDefined).toSet
+
+  override def part1(input: String): String = {
+    val graph = getGraph(input)
+    val zero = graph get 0
+    graph.nodes.count(_.pathTo(zero).isDefined).toString
+  }
+
+  override def part2(input: String): String = {
+    val graph = getGraph(input)
+    def groups(g: Graph[Int, DiEdge], count: Int = 0): Int = {
+      if (g.isEmpty) {
+        count
+      } else {
+        val node = g.nodes.toList.head
+        val group = findGroup(g)(node)
+        groups(g --! group, count + 1)
+      }
+    }
+    groups(graph).toString
+  }
+
+}

aoc/src/main/scala/aoc/y2017/package.scala

@@ -16,6 +16,7 @@ package object y2017 extends Year {
     "9" -> Day09,
     "10" -> Day10,
     "11" -> Day11,
+    "12" -> Day12,
     "25" -> Day25
   )
 
@@ -30,6 +31,7 @@ package object y2017 extends Year {
   }
 
   implicit class TupleInt2Ops(t: (Int, Int)) {
+
     def +(o: (Int, Int)): (Int, Int) = (t, o) match {
       case ((x1, y1), (x2, y2)) => (x1 + x2, y1 + y2)
     }

build.sbt

@@ -6,7 +6,8 @@ val sharedSettings = Seq(
   version      := "0.1.0",
   scalaVersion := "2.12.7",
   libraryDependencies ++= List(
-    "com.lihaoyi" %%% "fastparse" % "2.0.4",
+    "com.lihaoyi" %%% "fastparse"      % "2.0.4",
+    "org.scala-graph" %%% "graph-core" % "1.12.5",
   ),
   mainClass := Some("tf.bug.aoc.Main"),
 )