Day 5

Mix.install([
  {:req, "~> 0.3.2"},
  {:vega_lite, "~> 0.1.6"},
  {:kino_vega_lite, "~> 0.1.6"}
])

alias VegaLite, as: Vl

day = 5

aoc_session = System.fetch_env!("LB_AOC_SESSION")
input_url = "https://adventofcode.com/2022/day/#{day}/input"
{:ok, %{body: input}} = Req.get(input_url, headers: [cookie: "session=#{aoc_session}"])

Input

test_input = """
    [D]    
[N] [C]    
[Z] [M] [P]
 1   2   3 

move 1 from 2 to 1
move 3 from 1 to 3
move 2 from 2 to 1
move 1 from 1 to 2
"""

parse_move_str = fn str ->
  [_, move, _, from, _, to] = String.split(str, " ")
  lst = for i <- [move, from, to], do: String.to_integer(i)
  List.to_tuple(lst)
end

parse_row_str = fn row_str ->
  row_str
  |> String.graphemes()
  |> Enum.chunk_every(4)
  |> Enum.map(fn str ->
    str
    |> Enum.join()
    |> String.replace(~r/[\[\]\s]/, "")
  end)
end

add_crates_to_stacks = fn row_str, stacks ->
  row_str
  |> parse_row_str.()
  |> Enum.with_index(1)
  |> Enum.reject(fn {crate, _i} -> crate == "" end)
  |> Enum.reduce(stacks, fn {crate, i}, acc ->
    stack = Map.get(acc, i, [])
    Map.put(acc, i, stack ++ [crate])
  end)
end

create_stacks = fn crane_str ->
  crane_str
  |> String.split("\n", trim: true)
  |> Enum.filter(fn str -> str |> String.trim() |> String.starts_with?("[") end)
  |> Enum.reduce(%{}, fn row_str, stacks ->
    add_crates_to_stacks.(row_str, stacks)
  end)
end

Part 1

# input = test_input

[crane_str, move_list] = input |> String.split("\n\n", trim: true)

stacks = create_stacks.(crane_str)

final_configuration =
  move_list
  |> String.split("\n", trim: true)
  |> Enum.reduce(stacks, fn move_str, stacks ->
    {num, from, to} = parse_move_str.(move_str)
    from_stack = Map.get(stacks, from, [])
    to_stack = Map.get(stacks, to, [])
    {moving, rest} = Enum.split(from_stack, num)

    stacks
    |> Map.put(from, rest)
    |> Map.put(to, Enum.reverse(moving) ++ to_stack)
  end)

for({_, [ch | _]} <- final_configuration, do: ch)
|> Enum.join()

Part 2

# input = test_input

[crane_str, move_list] = input |> String.split("\n\n", trim: true)

stacks = create_stacks.(crane_str)

final_configuration =
  move_list
  |> String.split("\n", trim: true)
  |> Enum.reduce(stacks, fn move_str, stacks ->
    {num, from, to} = parse_move_str.(move_str)
    from_stack = Map.get(stacks, from, [])
    to_stack = Map.get(stacks, to, [])
    {moving, rest} = Enum.split(from_stack, num)

    stacks
    |> Map.put(from, rest)
    |> Map.put(to, moving ++ to_stack)
  end)

for({_, [ch | _]} <- final_configuration, do: ch)
|> Enum.join()