Here’s my attempt - new to Elixir for AOC 24
defmodule Aoc2024.Day2 do
# opts = [headers: [{"cookie", "session=#{System.fetch_env!("AOC_SESSION_COOKIE")}"}]]
# input = Req.get!("https://adventofcode.com/2024/day/2/input", opts).body
def part_1(input) do
input
|> String.split("\n", trim: true)
|> Enum.map(&convert_to_int_list/1)
|> Enum.map(&check_report/1)
|> Enum.count(fn s -> elem(s, 0) == :safe end)
end
def part_2(input) do
input
|> String.split("\n", trim: true)
|> Enum.map(&convert_to_int_list/1)
|> Enum.map(&safe_combinations?/1)
|> Enum.count(fn s -> s == true end)
end
defp convert_to_int_list(readings) do
readings
|> String.split()
|> Enum.map(&String.to_integer/1)
end
defp safe_combinations?(reading) do
[reading | (for idx <- (0..length(reading) - 1), do: List.delete_at(reading, idx))]
|> Enum.map(&check_report/1)
|> Enum.any?(fn s -> elem(s, 0) == :safe end)
end
defp check_report(reading) do
reading
|> Enum.reduce({:unknown}, fn x, acc ->
case acc do
{:unsafe} ->
{:unsafe}
{:unknown} ->
{:safe, :unknown, x}
{:safe, :unknown, prev} when prev < x and abs(prev - x) < 4 ->
{:safe, :increasing, x}
{:safe, :unknown, prev} when prev > x and abs(prev - x) < 4 ->
{:safe, :decreasing, x}
{:safe, :increasing, prev} when prev < x and abs(prev - x) < 4 ->
{:safe, :increasing, x}
{:safe, :decreasing, prev} when prev > x and abs(prev - x) < 4 ->
{:safe, :decreasing, x}
_ ->
{:unsafe}
end
end)
end
end
