Day02

Setup

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

sample_text = Kino.Input.textarea("sample")

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

sample = Kino.Input.read(sample_text)
input = Kino.Input.read(input_text)

defmodule Shared do
  def parse_line(line) do
    line
    |> String.split(": ")
    |> then(&[parse_password(tl(&1)) | parse_policy(hd(&1))])
    |> List.to_tuple()
  end

  defp parse_policy(string) do
    string
    |> String.split(["-", " "])
    |> clean_policy()
  end

  defp clean_policy([min, max, char]) do
    [String.to_integer(min), String.to_integer(max), char]
  end

  defp parse_password([string]), do: string

  def validate_a({pass, min, max, char}) do
    pass
    |> String.split(char)
    |> Enum.count()
    |> then(&amp;(min <= &amp;1 - 1 and max >= &amp;1 - 1))
  end

  def validate_b({pass, pos1, pos2, char}) do
    pass
    |> then(&amp;{String.at(&amp;1, pos1 - 1) == char, String.at(&amp;1, pos2 - 1) == char})
    |> then(&amp;((elem(&amp;1, 0) or elem(&amp;1, 1)) and !(elem(&amp;1, 0) and elem(&amp;1, 1))))

    # Is there no xor operator??
  end
end

part a

input
|> String.split("\n", trim: true)
|> Enum.map(&Shared.parse_line/1)
|> Enum.map(&Shared.validate_a/1)
|> Enum.filter(& &1)
|> Enum.count()

part b

input
|> String.split("\n", trim: true)
|> Enum.map(&Shared.parse_line/1)
|> Enum.map(&Shared.validate_b/1)
|> Enum.filter(& &1)
|> Enum.count()