Day 3

Mix.install([{:kino, "~> 0.5.0"}])

Input

input = """
vJrwpWtwJgWrhcsFMMfFFhFp
jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
PmmdzqPrVvPwwTWBwg
wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
ttgJtRGJQctTZtZT
CrZsJsPPZsGzwwsLwLmpwMDw
"""

input = Kino.Input.textarea("Input file here:")

input = Kino.Input.read(input)

Part 1

priority = fn c ->
  priorities = Map.new(Enum.zip(?a..?z, 1..26) ++ Enum.zip(?A..?Z, 27..52))
  priorities[c]
end

common = fn s ->
  len = div(String.length(s), 2)

  {first, second} =
    s
    |> to_charlist()
    |> Enum.map(priority)
    |> Enum.split(len)

  MapSet.intersection(MapSet.new(first), MapSet.new(second)) |> Enum.sum()
end

common.("vJrwpWtwJgWrhcsFMMfFFhFp")

input
|> String.split()
|> Enum.map(common)
|> Enum.sum()

Part 2

common = fn list ->
  list
  |> Enum.map(&to_charlist/1)
  |> Enum.map(&Enum.map(&1, priority))
  |> Enum.map(&MapSet.new/1)
  |> Enum.reduce(&MapSet.intersection/2)
  |> Enum.sum()
end

18 =
  common.(["vJrwpWtwJgWrhcsFMMfFFhFp", "jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL", "PmmdzqPrVvPwwTWBwg"])

input
|> String.split()
|> Enum.chunk_every(3)
|> Enum.map(common)
|> Enum.sum()