2024/23 remove process dictionary use

elixir/livebook/2024/day23.livemd

@@ -52,32 +52,22 @@ defmodule LANGraph do
   
   @empty MapSet.new([])
   def bron_kerbosch(g) do
-    Process.delete(:maximal)
     neighbor_set = fn v ->
-      n = neighbors(g, v)  |> MapSet.new()
-      n
+      neighbors(g, v)  |> MapSet.new()
     end
-    bron_kerbosch(MapSet.new, g.nodes, MapSet.new, neighbor_set)
+    bron_kerbosch(MapSet.new, g.nodes, MapSet.new, neighbor_set, [])
   end
   
-  def bron_kerbosch(r,o,o,_) when o == @empty do
-    Process.put(
-        :maximal,
-        case Process.get(:maximal) do
-          nil -> [r]
-          l -> [r | l]
-        end
-    )
-  end
-  def bron_kerbosch(_,o,_,_) when o == @empty, do: @empty
-  def bron_kerbosch(r,p,x,n) do
+  def bron_kerbosch(r,o,o,_,acc) when o == @empty, do: [r | acc]
+  def bron_kerbosch(_,o,_,_,acc) when o == @empty, do: acc
+  def bron_kerbosch(r,p,x,n,acc) do
     for v <- p,
       n_v = n.(v),
-      reduce: {p, x} do
-      {p, x} -> 
-        bron_kerbosch(MapSet.put(r, v), MapSet.intersection(p, n_v), MapSet.intersection(x, n_v), n)
-        {p |> MapSet.delete(v), x |> MapSet.put(v)}
-    end
+      reduce: {p, x, acc} do
+      {p, x, acc} -> 
+        acc = bron_kerbosch(MapSet.put(r, v), MapSet.intersection(p, n_v), MapSet.intersection(x, n_v), n, acc)
+        {p |> MapSet.delete(v), x |> MapSet.put(v), acc}
+      end |> elem(2)
   end
 
   def parse(input), do: input 
@@ -104,8 +94,6 @@ defmodule LANGraph do
     input
     |> parse() 
     |> bron_kerbosch()
-    
-    Process.get(:maximal)
     |> Enum.max_by(&MapSet.size/1)
     |> Stream.map(&Atom.to_string/1)
     |> Enum.sort