solve 2024 day 13 pt. 1

2024/lib/2024/13.ex

@@ -0,0 +1,57 @@
+import AOC
+
+aoc 2024, 13 do
+  def p1(input) do
+    input
+    |> read_machines()
+    |> Enum.map(&solve/1)
+    |> Enum.filter(&match?({:solution, a, b} when a <= 100 and b <= 100, &1))
+    |> Enum.map(&tokens_for_solution/1)
+    |> Enum.sum()
+  end
+
+  def p2(_input) do
+  end
+
+  defp solve(%{a: {xa, ya}, b: {xb, yb}, goal: {x, y}}) do
+    [a, b] =
+      [[xa, xb], [ya, yb]]
+      |> Nx.tensor()
+      |> Nx.LinAlg.solve(Nx.tensor([x, y]))
+      |> Nx.round()
+      |> Nx.to_list()
+      |> Enum.map(&trunc/1)
+
+    if xa * a + xb * b == x and ya * a + yb * b == y do
+      {:solution, a, b}
+    else
+      :impossible
+    end
+  end
+
+  defp tokens_for_solution({:solution, a, b}) do
+    3 * a + b
+  end
+
+  # defp valid_solution?()
+
+  ## input
+
+  defp read_machines(str) do
+    ~r/Button A: X\+(\d+), Y\+(\d+)\nButton B: X\+(\d+), Y\+(\d+)\nPrize: X=(\d+), Y=(\d+)/m
+    |> Regex.scan(
+      str,
+      capture: :all_but_first
+    )
+    |> Enum.map(fn strings ->
+      [xa, ya, xb, yb, x, y] =
+        Enum.map(strings, &String.to_integer/1)
+
+      %{
+        a: {xa, ya},
+        b: {xb, yb},
+        goal: {x, y}
+      }
+    end)
+  end
+end

2024/mix.exs

@@ -23,6 +23,7 @@ defmodule Aoc2024.MixProject do
     [
       {:advent_of_code_utils, "~> 4.0"},
       {:nimble_parsec, "~> 1.4"},
+      {:nx, "~> 0.9.2"},
       {:styler, "~> 1.2", only: [:dev, :test], runtime: false}
     ]
   end

2024/mix.lock

@@ -1,7 +1,10 @@
 %{
   "advent_of_code_utils": {:hex, :advent_of_code_utils, "4.0.1", "591073a49600cbceae6d92e0fb2d2c56b59f6d383851e2a7c00c3bf0e4f33f4f", [:mix], [{:floki, "~> 0.34", [hex: :floki, repo: "hexpm", optional: false]}, {:tz, "~> 0.26", [hex: :tz, repo: "hexpm", optional: false]}], "hexpm", "684d016883d7b5443d9d22abc34013fb6f1d5d9ff114859a40890545a570eec8"},
+  "complex": {:hex, :complex, "0.5.0", "af2d2331ff6170b61bb738695e481b27a66780e18763e066ee2cd863d0b1dd92", [:mix], [], "hexpm", "2683bd3c184466cfb94fad74cbfddfaa94b860e27ad4ca1bffe3bff169d91ef1"},
   "floki": {:hex, :floki, "0.36.3", "1102f93b16a55bc5383b85ae3ec470f82dee056eaeff9195e8afdf0ef2a43c30", [:mix], [], "hexpm", "fe0158bff509e407735f6d40b3ee0d7deb47f3f3ee7c6c182ad28599f9f6b27a"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.4.0", "51f9b613ea62cfa97b25ccc2c1b4216e81df970acd8e16e8d1bdc58fef21370d", [:mix], [], "hexpm", "9c565862810fb383e9838c1dd2d7d2c437b3d13b267414ba6af33e50d2d1cf28"},
+  "nx": {:hex, :nx, "0.9.2", "17563029c01bf749aad3c31234326d7665abd0acc33ee2acbe531a4759f29a8a", [:mix], [{:complex, "~> 0.5", [hex: :complex, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "914d74741617d8103de8ab1f8c880353e555263e1c397b8a1109f79a3716557f"},
   "styler": {:hex, :styler, "1.2.1", "28f9e3d4b065c22575c56b8ae03d05188add1b21bec5ae664fc1551e2dfcc41b", [:mix], [], "hexpm", "71dc33980e530d21ca54db9c2075e646faa6e7b744a9d4a3dfb0ff01f56595f0"},
+  "telemetry": {:hex, :telemetry, "1.3.0", "fedebbae410d715cf8e7062c96a1ef32ec22e764197f70cda73d82778d61e7a2", [:rebar3], [], "hexpm", "7015fc8919dbe63764f4b4b87a95b7c0996bd539e0d499be6ec9d7f3875b79e6"},
   "tz": {:hex, :tz, "0.28.1", "717f5ffddfd1e475e2a233e221dc0b4b76c35c4b3650b060c8e3ba29dd6632e9", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:mint, "~> 1.6", [hex: :mint, repo: "hexpm", optional: true]}], "hexpm", "bfdca1aa1902643c6c43b77c1fb0cb3d744fd2f09a8a98405468afdee0848c8a"},
 }