Advent of Code 2021 day 03

Setup

Mix.install([
  {:kino, github: "livebook-dev/kino"},
  {:nx, github: "elixir-nx/nx", sparse: "nx"}
])

input = Kino.Input.textarea("Please add your input:")

Part 1

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, "", trim: true))
|> List.zip()
|> Enum.map(&Tuple.to_list/1)
|> Enum.map(&Enum.frequencies/1)
|> Enum.map(&Map.values/1)
|> Enum.map(fn [zeros, ones] -> if zeros > ones, do: ["0", "1"], else: ["1", "0"] end)
|> List.zip()
|> Enum.map(&Tuple.to_list/1)
|> Enum.map(&Enum.join/1)
|> Enum.map(&String.to_integer(&1, 2))
|> Enum.reduce(1, &Kernel.*/2)

Part 2

defmodule Day3 do
  def sleve(_bit, list, _flip) when length(list) == 1, do: list

  def sleve(bit, list, flip) do
    ones =
      list
      |> Enum.map(&String.at(&1, bit))
      |> Enum.count(fn i -> i == "1" end)

    target = if length(list) - ones > ones, do: "0", else: "1"
    filter_fn = if flip, do: &Enum.reject/2, else: &Enum.filter/2
    filter_fn.(list, fn i -> String.at(i, bit) == target end)
  end
end

data =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)

bits = data |> Enum.at(0) |> String.length()

oxygen =
  Enum.reduce(0..(bits - 1), data, &Day3.sleve(&1, &2, false))
  |> Enum.at(0)
  |> String.to_integer(2)

co2 =
  Enum.reduce(0..(bits - 1), data, &Day3.sleve(&1, &2, true))
  |> Enum.at(0)
  |> String.to_integer(2)

oxygen * co2