Efficiency improvements for 2024 Day 22 Part 2

2024/day22.exs

@@ -22,11 +22,10 @@ defmodule Day22 do
   def part2(input) do
     input
     |> Enum.map(fn secret ->
-      secret
-      |> Stream.iterate(&next/1)
-      |> Stream.map(&bananas/1)
-      |> Stream.take(2000)
-      |> Stream.chunk_every(5, 1, :discard)
+      1..2000
+      |> Enum.map_reduce(secret, fn _, secret -> {rem(secret, 10), next(secret)} end)
+      |> elem(0)
+      |> Enum.chunk_every(5, 1, :discard)
       |> Enum.reduce(%{}, fn [a, b, c, d, bananas], changes ->
         Map.put_new(changes, {b - a, c - b, d - c, bananas - d}, bananas)
       end)
@@ -36,10 +35,6 @@ defmodule Day22 do
     |> elem(1)
   end
 
-  def bananas(secret) do
-    secret |> Integer.to_string() |> String.last() |> String.to_integer()
-  end
-
   def input do
     with [input_filename] <- System.argv(),
          {:ok, input} <- File.read(input_filename) do