Day 03

Mix.install([
  {:kino, "~> 0.7.0"}
])

example_input =
  Kino.Input.textarea("example input:")
  |> Kino.render()

real_input = Kino.Input.textarea("real input:")

Common

priorities =
  Enum.concat(?a..?z, ?A..?Z)
  |> Enum.zip(1..52)
  |> Enum.into(%{})

parse = fn input ->
  input
  |> Kino.Input.read()
  |> String.split("\n")
  |> Enum.map(&to_charlist/1)
end

Part 1

real_input
|> then(parse)
|> Enum.map(fn rucksack ->
  rucksack
  |> Enum.split(div(length(rucksack), 2))
  |> Tuple.to_list()
  |> Enum.map(&MapSet.new/1)
  |> Enum.reduce(&MapSet.intersection(&1, &2))
  |> MapSet.to_list()
  |> List.first()
  |> then(&priorities[&1])
end)
|> Enum.sum()

Part 2

real_input
|> then(parse)
|> Enum.chunk_every(3)
|> Enum.map(fn list ->
  list
  |> Enum.map(&MapSet.new/1)
  |> Enum.reduce(&MapSet.intersection(&1, &2))
  |> MapSet.to_list()
  |> List.first()
  |> then(&priorities[&1])
end)
|> Enum.sum()