Day 5

Day 5: Supply Stacks

Day 5: Supply Stacks

Input

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
"""

Part 1

defmodule Stack do
  def push("", stack) do
    stack
  end

  def push(e, stack) do
    [e | stack]
  end

  def pop([]), do: {"", []}

  def pop([head | tail]), do: {head, tail}
end

[crates, [""], procedures, [""]] =
  input
  |> String.split("\n")
  |> Enum.chunk_by(&(&1 == ""))

crates =
  crates
  |> Enum.take(Enum.count(crates) - 1)
  |> Enum.map(fn line ->
    String.split(line, [" "])
    |> Enum.reduce({[], 0}, fn
      "", {acc_list, acc_cnt} ->
        acc_cnt = acc_cnt + 1

        if acc_cnt >= 4 do
          {acc_list ++ [""], 0}
        else
          {acc_list, acc_cnt}
        end

      <<"[", s, "]">>, {acc_list, _acc_cnt} ->
        {acc_list ++ [s], 0}
    end)
    |> elem(0)
  end)
  |> IO.inspect()

[top | _] = crates
rows = Enum.count(top) |> IO.inspect()

crates_map =
  crates
  |> Enum.map(&Enum.with_index/1)
  |> Enum.with_index()
  |> Enum.reduce(%{}, fn {list, i}, acc ->
    list
    |> Enum.reduce(acc, fn {crate, j}, acc2 ->
      Map.merge(acc2, %{{i, j} => crate})
    end)
  end)
  |> IO.inspect()

stacks_of_crates =
  for j <- 0..(rows - 1), i <- (Enum.count(crates) - 1)..0, reduce: %{} do
    acc ->
      Map.update(acc, j, Stack.push(crates_map[{i, j}], []), &Stack.push(crates_map[{i, j}], &1))
  end

procedures
|> Enum.map(fn procedure ->
  ["move", cnt, "from", from, "to", to] = String.split(procedure, " ")
  {String.to_integer(cnt), String.to_integer(from) - 1, String.to_integer(to) - 1}
end)
|> Enum.reduce(stacks_of_crates, fn {cnt, from, to}, acc ->
  1..cnt
  |> Enum.reduce(acc, fn _, acc2 ->
    IO.inspect(acc2)
    {e, from_stack} = Stack.pop(acc2[from])
    to_stack = Stack.push(e, acc2[to])
    acc2 |> Map.merge(%{from => from_stack}) |> Map.merge(%{to => to_stack}) |> IO.inspect()
  end)
end)
|> Enum.sort_by(fn {column, _stack} -> column end)
|> Enum.map(fn {_, [head | _]} -> head end)

Part 2

defmodule CrateMover9001 do
  def push(list, stack) do
    list ++ stack
  end

  def pop(stack, cnt), do: {Enum.take(stack, cnt), Enum.slice(stack, cnt..-1)}
end

procedures
|> Enum.map(fn procedure ->
  ["move", cnt, "from", from, "to", to] = String.split(procedure, " ")
  {String.to_integer(cnt), String.to_integer(from) - 1, String.to_integer(to) - 1}
end)
|> Enum.reduce(stacks_of_crates, fn {cnt, from, to}, acc ->
  {list, from_stack} = CrateMover9001.pop(acc[from], cnt)
  to_stack = CrateMover9001.push(list, acc[to])
  acc |> Map.merge(%{from => from_stack}) |> Map.merge(%{to => to_stack}) |> IO.inspect()
end)
|> Enum.sort_by(fn {column, _stack} -> column end)
|> Enum.map(fn {_, [head | _]} -> head end)