Day 8

Mix.install([
  {:kino, "~> 0.6.2"}
])

Input

input = Kino.Input.textarea("Dump your digits")

Part 1

Kino.Input.read(input)
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, " | "))
|> IO.inspect()
|> Enum.map(fn [_, nums] ->
  String.split(nums, " ") |> Enum.count(fn x -> String.length(x) in [2, 3, 4, 7] end)
end)
|> Enum.sum()

Part 2

numbers =
  Kino.Input.read(input)
  |> String.split("\n", trim: true)
  |> Enum.map(&String.split(&1, " | "))
  |> Enum.map(fn [a, b] -> [String.split(a), String.split(b)] end)

[[codes, number] | _] = numbers

for [codes, number] <- numbers do
  digits = codes |> Enum.group_by(&amp;byte_size/1, &amp;String.to_charlist/1)

  %{
    2 => [one],
    3 => [seven],
    4 => [four],
    5 => two_three_five,
    6 => zero_six_nine,
    7 => [eight]
  } = digits

  %{true: [nine], false: zero_six} = Enum.group_by(zero_six_nine, &amp;(four -- &amp;1 == []))
  %{true: three_five, false: [two]} = Enum.group_by(two_three_five, &amp;(&amp;1 -- nine == []))
  %{true: [three], false: [five]} = Enum.group_by(three_five, &amp;(seven -- &amp;1 == []))
  %{true: [zero], false: [six]} = Enum.group_by(zero_six, &amp;(seven -- &amp;1 == []))

  eq = fn a, b -> a -- b == [] &amp;&amp; b -- a == [] end

  # IO.inspect({one,two,three,four,five,six,seven,eight,nine,zero})

  digit = fn s ->
    x = to_charlist(s)

    cond do
      eq.(x, one) -> 1
      eq.(x, two) -> 2
      eq.(x, three) -> 3
      eq.(x, four) -> 4
      eq.(x, five) -> 5
      eq.(x, six) -> 6
      eq.(x, seven) -> 7
      eq.(x, eight) -> 8
      eq.(x, nine) -> 9
      eq.(x, zero) -> 0
    end
  end

  number |> Enum.map(digit) |> Integer.undigits()
end
|> Enum.sum()