Solve 2023/25

Author: code-shoily

lib/2023/day_25.ex

@@ -3,77 +3,53 @@ defmodule AdventOfCode.Y2023.Day25 do
   --- Day 25: Snowverload ---
   Problem Link: https://adventofcode.com/2023/day/25
   Difficulty: xl
-  Tags: graph min-cut probabilistic refactor not-fast-enough
+  Tags: graph min-cut deterministic refactor
   """
   alias AdventOfCode.Helpers.{InputReader, Transformers}
+  alias Yog.Builder.Labeled
+  alias Yog.Flow.MinCut
+  alias Yog.Flow.MinCutResult
 
   def input, do: InputReader.read_from_file(2023, 25)
 
   def run(input \\ input()) do
-    input = parse(input)
+    builder = parse(input)
+    graph = Labeled.to_graph(builder)
 
-    {run_1(input), run_2(input)}
+    {run_1(graph), run_2(graph)}
   end
 
-  defp run_1(input) do
-    Stream.repeatedly(fn -> contract(input) end)
-    |> Enum.find(fn g1 -> cut_size(g1, input) == 3 end)
-    |> Map.keys()
-    |> Enum.map(&String.length/1)
-    |> Enum.product_by(&div(&1, 3))
+  defp run_1(graph) do
+    # Stoer-Wagner finds the global minimum cut in an undirected graph.
+    # In this problem, we are guaranteed that the global min-cut size is 3.
+    result = MinCut.global_min_cut(graph)
+
+    # Use the optimized partition_product helper
+    MinCutResult.partition_product(result)
   end
 
   defp run_2(_), do: "🎉"
 
+  @doc """
+  Parses the input into a Yog Labeled builder.
+  Each line defines a node and its connections: `jqt: rhn xhk nvd`
+  """
   def parse(input) do
-    for line <- Transformers.lines(input), reduce: %{} do
-      graph ->
-        [u | connected] = String.split(line, [":", " "], trim: true)
-
-        for v <- connected, reduce: graph do
-          edges ->
-            edges
-            |> Map.update(u, MapSet.new([v]), &MapSet.put(&1, v))
-            |> Map.update(v, MapSet.new([u]), &MapSet.put(&1, u))
-        end
-    end
-  end
-
-  def cut_size(g, h) do
-    for {key, _} <- g do
-      key
-      |> String.to_charlist()
-      |> Enum.chunk_every(3)
-      |> Enum.map(&to_string/1)
-    end
-    |> then(fn [us, vs] ->
-      for u <- us, _ <- MapSet.intersection(h[u], MapSet.new(vs)), reduce: 0 do
-        acc -> acc + 1
+    data = Transformers.lines(input)
+
+    Enum.reduce(data, Labeled.undirected(), fn line, builder ->
+      case String.split(line, ": ", trim: true) do
+        [source, dests] ->
+          dests
+          |> String.split(" ", trim: true)
+          |> Enum.reduce(builder, fn target, b ->
+            Labeled.add_edge(b, source, target, 1)
+          end)
+
+        _ ->
+          builder
       end
     end)
   end
-
-  def contract(graph) when map_size(graph) == 2, do: graph
-
-  def contract(graph) do
-    {u, u_edges} = Enum.random(graph)
-    v = Enum.random(u_edges)
-
-    u_edges = u_edges |> MapSet.delete(v)
-    v_edges = graph[v] |> MapSet.delete(u)
-    u_v_edges = MapSet.union(u_edges, v_edges)
-    uv = u <> v
-
-    Enum.reduce(u_edges, graph, fn c, acc ->
-      Map.update!(acc, c, &MapSet.put(MapSet.delete(&1, u), uv))
-    end)
-    |> then(fn graph ->
-      Enum.reduce(v_edges, graph, fn c, acc ->
-        Map.update!(acc, c, &MapSet.put(MapSet.delete(&1, v), uv))
-      end)
-      |> Map.drop([u, v])
-      |> Map.put(uv, u_v_edges)
-    end)
-    |> contract()
-  end
 end
+

mix.exs

@@ -26,7 +26,7 @@ defmodule AdventOfCode.MixProject do
       {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
       {:floki, "~> 0.36"},
       {:httpoison, "~> 2.2"},
-      {:yog_ex, "~> 0.90.0"},
+      {:yog_ex, github: "code-shoily/yog_ex", branch: "main"},
       {:aja, "~> 0.7"},
       {:topo, "~> 1.0"},
       {:rustler, "~> 0.35"}

mix.lock

@@ -20,5 +20,5 @@
   "topo": {:hex, :topo, "1.0.3", "8073215c392ad0aced6505a5a281da4af613f5608f6db826635b96fe7a2f4240", [:mix], [{:geo, "~> 3.1 or ~> 4.0", [hex: :geo, repo: "hexpm", optional: false]}, {:seg_seg, "~> 1.0", [hex: :seg_seg, repo: "hexpm", optional: false]}, {:vector, "~> 1.0", [hex: :vector, repo: "hexpm", optional: false]}], "hexpm", "d37720895ec08848d33960deb94f00254834e0a2398618461b800f142c84577c"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.1", "a48703a25c170eedadca83b11e88985af08d35f37c6f664d6dcfb106a97782fc", [:rebar3], [], "hexpm", "b3a917854ce3ae233619744ad1e0102e05673136776fb2fa76234f3e03b23642"},
   "vector": {:hex, :vector, "1.1.0", "0789b5e00e9c551d8d5880acab9a8f44ed46690d083af397018bf0c7f30c1092", [:mix], [], "hexpm", "48b0a800ec88e55b12c689b09100e4c9ba41ea1befb459221c085a4e70040696"},
-  "yog_ex": {:hex, :yog_ex, "0.90.0", "07c66979ff547faea560f1a40c4613071cd491651a0b5a1d81d75cef13388153", [:mix], [{:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}, {:saxy, "~> 1.5", [hex: :saxy, repo: "hexpm", optional: false]}], "hexpm", "9d90a291fe40a535b525003a831347808f8a1120ced64409210f7efef1c172b3"},
+  "yog_ex": {:git, "https://github.com/code-shoily/yog_ex.git", "74dd8f69469cb4cb2fe2c197181b2c3d2188b2f3", [branch: "main"]},
 }