Advent of code day 05

Mix.install([
  {:kino, "~> 0.5.0"}
])

Setup input

input = Kino.Input.textarea("Please paste your input file:")

[stacks, moves | []] =
  input
  |> Kino.Input.read()
  |> String.split(["\n\n"])

moves =
  moves
  |> String.split("\n")
  |> Enum.map(&String.split(&1, " "))
  |> Enum.map(fn [_, quantity, _, origin_stack, _, destiny_stack | []] ->
    {String.to_integer(quantity), String.to_integer(origin_stack),
     String.to_integer(destiny_stack)}
  end)

[_keys | stacks] = stacks |> String.split("\n") |> Enum.reverse()

stacks =
  stacks
  |> Enum.map(fn stack ->
    stack
    |> String.graphemes()
    |> Enum.chunk_every(3, 4, :discard)
    |> Enum.with_index(1)
  end)
  |> List.flatten()
  |> Enum.filter(fn {[_a, value | _tail], _key} -> value != " " end)
  |> Enum.reduce(%{}, fn {[_a, value, _c], key}, acc ->
    new_list = [value | Map.get(acc, key, [])]
    Map.put(acc, key, new_list)
  end)

Part 01

stack_after_moves =
  Enum.reduce(moves, stacks, fn {count, from, to}, crates ->
    {take, remain} = Enum.split(crates[from], count) |> IO.inspect()

    Map.put(crates, from, remain)
    |> Map.put(to, Enum.reverse(take) ++ crates[to])
  end)

key =
  Enum.reduce(stack_after_moves, "", fn {_key, [head | _]}, acc ->
    acc <> head
  end)

Part 02

stack_after_moves =
  Enum.reduce(moves, stacks, fn {count, from, to}, crates ->
    {take, remain} = Enum.split(crates[from], count)

    Map.put(crates, from, remain)
    |> Map.put(to, take ++ crates[to])
  end)

key =
  Enum.reduce(stack_after_moves, "", fn {_key, [head | _]}, acc ->
    acc <> head
  end)