Here are the solutions I came up with for today:
Part 1:
defmodule Day3.Part1 do
def solve() do
File.stream!("03/input.txt")
|> Enum.reduce(
0,
fn line, acc ->
acc +
(~r/mul\((\d{1,3}),(\d{1,3})\)/
|> Regex.scan(line |> String.trim(), capture: :all_but_first)
|> Enum.reduce(
0,
fn [a, b], acc -> acc + String.to_integer(a) * String.to_integer(b) end
))
end
)
|> IO.puts()
end
end
Day3.Part1.solve()
Part 2:
defmodule Day3.Part2 do
defp sum_part(part) do
~r/mul\((\d{1,3}),(\d{1,3})\)/
|> Regex.scan(part, capture: :all_but_first)
|> Enum.reduce(
0,
fn [a, b], acc -> acc + String.to_integer(a) * String.to_integer(b) end
)
end
def solve() do
File.stream!("03/input.txt")
|> Enum.reduce(
{0, true},
fn line, {acc, start_enabled?} ->
{acc +
(line
|> String.trim()
|> String.split("do")
|> (fn parts ->
if start_enabled? do
parts
else
parts
|> Enum.drop(1)
end
end).()
|> Enum.filter(&(not String.starts_with?(&1, "n't()")))
|> Enum.map(&sum_part/1)
|> List.to_tuple()
|> Tuple.sum()),
~r/do\(\)/
|> Regex.scan(line, capture: :all, return: :index)
|> List.last()
|> List.last()
|> elem(0) >
~r/don't\(\)/
|> Regex.scan(line, capture: :all, return: :index)
|> List.last()
|> List.last()
|> elem(0)}
end
)
|> elem(0)
|> IO.puts()
end
end
Day3.Part2.solve()
