Extract BronKerbosch to library

Author: sim642

src/main/scala/eu/sim642/adventofcode2018/Day23.scala

@@ -4,6 +4,7 @@ import eu.sim642.adventofcodelib.box.{Box3, Box4}
 import eu.sim642.adventofcodelib.pos.Pos3
 import eu.sim642.adventofcodelib.pos.Pos4
 import eu.sim642.adventofcodelib.IntegralImplicits.*
+import eu.sim642.adventofcodelib.graph.BronKerbosch
 
 import scala.collection.mutable
 import scala.util.boundary
@@ -40,35 +41,9 @@ object Day23 {
   }
 
   object NaiveCliquePart2Solution extends Part2Solution {
-    def maximumClique(neighbors: Map[Nanobot, Set[Nanobot]]): Set[Nanobot] = {
-      var best: Set[Nanobot] = Set.empty
-
-      def bronKerbosh(r: Set[Nanobot], p: Set[Nanobot], x: Set[Nanobot]): Unit = {
-        if (p.isEmpty && x.isEmpty) {
-          //println(r)
-          if (r.size > best.size)
-            best = r
-        }
-        else {
-          //val u = p.headOption.getOrElse(x.head)
-          val u = (p ++ x).maxBy(neighbors(_).size) // pivot on highest degree
-          var p2 = p
-          var x2 = x
-          for (v <- p -- neighbors(u)) {
-            bronKerbosh(r + v, p2 intersect neighbors(v), x2 intersect neighbors(v))
-            p2 -= v
-            x2 += v
-          }
-        }
-      }
-
-      bronKerbosh(Set.empty, neighbors.keySet, Set.empty)
-      best
-    }
-
     def maximumOverlap(nanobots: Seq[Nanobot]): Set[Nanobot] = {
       val neighbors: Map[Nanobot, Set[Nanobot]] = nanobots.map(nanobot1 => nanobot1 -> nanobots.filter(nanobot2 => nanobot2 != nanobot1 && nanobot1.overlaps(nanobot2)).toSet).toMap
-      maximumClique(neighbors)
+      BronKerbosch.maximumClique(neighbors)
     }
 
     def closestMostNanobots(nanobots: Seq[Nanobot]): Int = {

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

@@ -1,5 +1,7 @@
 package eu.sim642.adventofcode2024
 
+import eu.sim642.adventofcodelib.graph.BronKerbosch
+
 object Day23 {
 
   type Computer = String
@@ -16,37 +18,9 @@ object Day23 {
 
   def count3CliquesT(edges: Set[Edge]): Int = find3Cliques(edges).count(_.exists(_.startsWith("t")))
 
-  // copied from 2018 day 23
-  // TODO: move to library
-  def maximumClique(neighbors: Map[Computer, Set[Computer]]): Set[Computer] = {
-    var best: Set[Computer] = Set.empty
-
-    def bronKerbosh(r: Set[Computer], p: Set[Computer], x: Set[Computer]): Unit = {
-      if (p.isEmpty && x.isEmpty) {
-        //println(r)
-        if (r.size > best.size)
-          best = r
-      }
-      else {
-        //val u = p.headOption.getOrElse(x.head)
-        val u = (p ++ x).maxBy(neighbors(_).size) // pivot on highest degree
-        var p2 = p
-        var x2 = x
-        for (v <- p -- neighbors(u)) {
-          bronKerbosh(r + v, p2 intersect neighbors(v), x2 intersect neighbors(v))
-          p2 -= v
-          x2 += v
-        }
-      }
-    }
-
-    bronKerbosh(Set.empty, neighbors.keySet, Set.empty)
-    best
-  }
-
   def maximumClique(edges: Set[Edge]): Set[Computer] = {
     val neighbors = (edges ++ edges.map(_.swap)).groupMap(_._1)(_._2)
-    maximumClique(neighbors)
+    BronKerbosch.maximumClique(neighbors)
   }
 
   def lanPartyPassword(edges: Set[Edge]): String = {

src/main/scala/eu/sim642/adventofcodelib/graph/BronKerbosch.scala

@@ -0,0 +1,31 @@
+package eu.sim642.adventofcodelib.graph
+
+object BronKerbosch {
+
+  // moved from 2018 day 23
+  def maximumClique[A](neighbors: Map[A, Set[A]]): Set[A] = {
+    var best: Set[A] = Set.empty
+
+    def bronKerbosch(r: Set[A], p: Set[A], x: Set[A]): Unit = {
+      if (p.isEmpty && x.isEmpty) {
+        //println(r)
+        if (r.size > best.size)
+          best = r
+      }
+      else {
+        //val u = p.headOption.getOrElse(x.head)
+        val u = (p ++ x).maxBy(neighbors(_).size) // pivot on highest degree
+        var p2 = p
+        var x2 = x
+        for (v <- p -- neighbors(u)) {
+          bronKerbosch(r + v, p2 intersect neighbors(v), x2 intersect neighbors(v))
+          p2 -= v
+          x2 += v
+        }
+      }
+    }
+
+    bronKerbosch(Set.empty, neighbors.keySet, Set.empty)
+    best
+  }
+}