add 2024 day 13

elixir/livebook/2024/day13.livemd

@@ -0,0 +1,44 @@
+# AOC 2024 Day 13
+
+```elixir
+Mix.install([
+  {:nx, "0.9.2"}
+])
+```
+
+## Section
+
+```elixir
+input = """
+"""
+```
+
+```elixir
+for {a, b} <- (for line <- (input |> String.trim() |> String.split("\n")), reduce: {[], []} do
+  {vecs, matrices} = acc -> 
+   case line do
+     "Button " <> rest ->
+       [[_, a, b]] = Regex.scan(~r/[AB]: X\+(\d+), Y\+(\d+)/, rest)
+       v = [a, b] |> Enum.map(&String.to_integer(&1))
+       {[v | vecs], matrices}
+     "Prize: " <> rest ->
+       [[_, a, b]] = Regex.scan(~r/X=(\d+), Y=(\d+)/, rest)
+       v = [a, b] |> Enum.map(&String.to_integer(&1))
+       a = Nx.tensor(vecs, type: :f64) |> Nx.transpose()
+       b = Nx.tensor(v |> Enum.map(&(&1+10000000000000)), type: :f64)
+       {[], [{a, b} | matrices]}
+     _ -> acc
+   end
+    end |> elem(1)),
+    c = Nx.LinAlg.invert(a) |> Nx.dot(b)  |> Nx.round(),
+    b_prime = Nx.dot(
+        a, c
+    ) |> Nx.round() |> Nx.as_type(:f64),
+  c = Nx.as_type(c, :s64),
+    b == b_prime,
+  reduce: Nx.tensor(0, type: :s64)
+  do
+    acc2 ->
+      c |> Nx.dot(Nx.tensor([1, 3], type: :s64)) |> Nx.add(acc2)
+  end 
+```