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Commit fe45dcf

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Solve 2024 day 23 part 2
1 parent 8340161 commit fe45dcf

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‎src/main/scala/eu/sim642/adventofcode2024/Day23.scala

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@@ -16,6 +16,44 @@ object Day23 {
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def count3CliquesT(edges: Set[Edge]): Int = find3Cliques(edges).count(_.exists(_.startsWith("t")))
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// copied from 2018 day 23
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// TODO: move to library
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def maximumClique(neighbors: Map[Computer, Set[Computer]]): Set[Computer] = {
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var best: Set[Computer] = Set.empty
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def bronKerbosh(r: Set[Computer], p: Set[Computer], x: Set[Computer]): Unit = {
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if (p.isEmpty && x.isEmpty) {
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//println(r)
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if (r.size > best.size)
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best = r
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}
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else {
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//val u = p.headOption.getOrElse(x.head)
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val u = (p ++ x).maxBy(neighbors(_).size) // pivot on highest degree
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var p2 = p
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var x2 = x
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for (v <- p -- neighbors(u)) {
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bronKerbosh(r + v, p2 intersect neighbors(v), x2 intersect neighbors(v))
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p2 -= v
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x2 += v
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}
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}
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}
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bronKerbosh(Set.empty, neighbors.keySet, Set.empty)
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best
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}
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def maximumClique(edges: Set[Edge]): Set[Computer] = {
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val neighbors = (edges ++ edges.map(_.swap)).groupMap(_._1)(_._2)
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maximumClique(neighbors)
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}
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def lanPartyPassword(edges: Set[Edge]): String = {
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val clique = maximumClique(edges)
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clique.toSeq.sorted.mkString(",")
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}
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def parseEdge(s: String): Edge = s match {
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case s"$from-$to" => (from, to)
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}
@@ -26,6 +64,7 @@ object Day23 {
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def main(args: Array[String]): Unit = {
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println(count3CliquesT(parseEdges(input)))
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println(lanPartyPassword(parseEdges(input)))
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// part 1: 2366 - too high (used contains 't' instead of startsWith 't')
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}

‎src/test/scala/eu/sim642/adventofcode2024/Day23Test.scala

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@@ -46,4 +46,12 @@ class Day23Test extends AnyFunSuite {
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test("Part 1 input answer") {
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assert(count3CliquesT(parseEdges(input)) == 1437)
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}
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test("Part 2 examples") {
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assert(lanPartyPassword(parseEdges(exampleInput)) == "co,de,ka,ta")
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}
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test("Part 2 input answer") {
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assert(lanPartyPassword(parseEdges(input)) == "da,do,gx,ly,mb,ns,nt,pz,sc,si,tp,ul,vl")
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}
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}

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