Day 01

Setup

defmodule Input do
  def read_all(input), do: read_all(input, IO.gets(input), [])

  defp read_all(_input, :eof, content), do: Enum.reverse(content)
  defp read_all(input, data, content), do: read_all(input, IO.gets(input), [data | content])
end

coerce_input_stream = fn
  input ->
    input
    |> Stream.map(&String.trim(&1))
    |> Stream.reject(&Kernel.==(&1, ""))
    |> Stream.map(&String.to_integer(&1))
end

example_input =
  Input.read_all("example_input")
  |> coerce_input_stream.()
  |> Enum.to_list()

count_increases = fn list ->
  {_, count} =
    Enum.reduce(list, {hd(list), 0}, fn curr, {prev, count} ->
      {curr, if(curr > prev, do: count + 1, else: count)}
    end)

  count
end

count_increases.(example_input)

real_input =
  Input.read_all("real_input")
  |> coerce_input_stream.()
  |> Enum.to_list()

count_increases.(real_input)

measurements_to_windows = fn
  measurements -> Stream.chunk_every(measurements, 3, 1, :discard)
end

sum_windows = fn
  windows -> Stream.map(windows, &Enum.sum(&1))
end

measurements_to_windows.(real_input)
|> sum_windows.()
|> Enum.to_list()
|> count_increases.()