AoC 2024 - Day 1

Mix.install([
  {:kino, "~> 0.14.2"}
])

Setup

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

Part 1

input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn row ->
    String.split(row, " ", trim: true)
  end)
|> Enum.reduce(%{first: [], second: []}, fn ([val1, val2], acc) ->
  %{
    first: [ String.to_integer(val1) | acc.first],
    second: [ String.to_integer(val2) | acc.second]
  }
end)
|> then( fn output ->
  %{
    first: Enum.sort(output.first),
    second: Enum.sort(output.second)
  }
end)
|> then( fn output ->
  output.first
  |> Enum.with_index()
  |> Enum.map(fn ({val, idx}) ->
    abs(val - Enum.at(output.second, idx))
  end)

end)
|> Enum.sum()

Part 2

input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn row ->
    String.split(row, " ", trim: true)
  end)
|> Enum.reduce(%{first: [], second: []}, fn ([val1, val2], acc) ->
  %{
    first: [ String.to_integer(val1) | acc.first],
    second: [ String.to_integer(val2) | acc.second]
  }
end)
|> then(fn output ->
  output.first
  |> Enum.reduce(0, fn(val, acc) ->
    count = output.second
      |> Enum.count(fn x ->
        x == val
      end)

    acc + val * count
  end)
end)