Day 5

Section

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
"""

path = "Projects/aoc/2022/day5.txt"
input = File.read!(path)

Part 1

defmodule Day5 do
  def part1(input) do
    {stacks, moves} =
      input
      |> String.split("\n", trim: true)
      |> Enum.split_while(fn x -> !String.contains?(x, "move") end)

    stacks
    |> load_stack()
    |> process(moves)
    |> output()
  end

  def part2(input) do
    {stacks, moves} =
      input
      |> String.split("\n", trim: true)
      |> Enum.split_while(fn x -> !String.contains?(x, "move") end)

    stacks
    |> load_stack()
    |> process_9001(moves)
    |> output()
  end

  def output(mp) do
    Map.values(mp)
    |> Enum.reduce('', fn [h | x], acc ->
      acc ++ h
    end)
  end

  def process_9001(stack, moves) do
    Enum.reduce(moves, stack, fn move, acc ->
      [_a, amnt, _b, from, _c, to] = String.split(move)

      {to_move, remaining} =
        Map.get(acc, String.to_integer(from)) |> Enum.split(String.to_integer(amnt))

      acc = Map.put(acc, String.to_integer(from), remaining)
      col = Map.get(acc, String.to_integer(to))
      Map.put(acc, String.to_integer(to), to_move |> Kernel.++(col))
    end)
  end

  def process(stack, moves) do
    Enum.reduce(moves, stack, fn move, acc ->
      [_a, amnt, _b, from, _c, to] = String.split(move)

      {to_move, remaining} =
        Map.get(acc, String.to_integer(from)) |> Enum.split(String.to_integer(amnt))

      acc = Map.put(acc, String.to_integer(from), remaining)
      col = Map.get(acc, String.to_integer(to))
      Map.put(acc, String.to_integer(to), to_move |> Enum.reverse() |> Kernel.++(col))
    end)
  end

  def parse_move(move) do
    String.split(move)
  end

  def parse_stack(x) do
    x
    |> String.to_charlist()
    |> Enum.with_index(0)
    |> Enum.filter(fn {x, _idx} ->
      x >= 65 &amp;&amp; x <= 90
    end)
    |> Enum.map(fn {x, idx} ->
      {x, div(idx, 4) + 1}
    end)
  end

  def load_stack(stacks) do
    stacks
    |> Enum.map(&amp;parse_stack(&amp;1))
    |> Enum.filter(fn x -> x != [] end)
    |> Enum.reverse()
    |> Enum.reduce(%{}, fn x, acc ->
      load_map(x, acc)
    end)
  end

  def load_map([], acc), do: acc

  def load_map([{crate, column} | t], acc) do
    col = Map.get(acc, column, [])
    load_map(t, Map.put(acc, column, [[crate] | col]))
  end
end

# Day5.part1(input)
Day5.part2(input)