Day 3: Rucksack Reorganization

Mix.install([:kino])

Part 1

input = Kino.Input.textarea("Input")

defmodule M do
  def score(str) do
    str
    |> String.split_at(div(String.length(str), 2))
    |> then(fn {l, r} ->
      MapSet.intersection(to_set(l), to_set(r))
    end)
    |> MapSet.to_list()
    |> hd()
    |> then(fn
      n when n >= ?a -> n - ?a + 1
      n when n >= ?A -> n - ?A + 1 + 26
    end)
  end

  defp to_set(str) do
    str
    |> String.to_charlist()
    |> MapSet.new()
  end
end

input
|> Kino.Input.read()
|> String.split()
|> Enum.map(&M.score/1)
|> Enum.sum()

Part 2

defmodule M do
  def score(group) do
    group
    |> Enum.map(&to_set/1)
    |> Enum.reduce(&MapSet.intersection/2)
    |> MapSet.to_list()
    |> hd()
    |> then(fn
      n when n >= ?a -> n - ?a + 1
      n when n >= ?A -> n - ?A + 1 + 26
    end)
  end

  defp to_set(str) do
    str
    |> String.to_charlist()
    |> MapSet.new()
  end
end

input
|> Kino.Input.read()
|> String.split()
|> Enum.chunk_every(3)
|> Enum.map(&M.score/1)
|> Enum.sum()