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|
defmodule Day4 do
def input() do
File.stream!("input/day4.in")
|> Stream.map(&String.trim/1)
|> Enum.sort()
end
def part1() do
{id, minute, _} =
input()
|> Enum.map(&parse_record_pattern/1)
|> Enum.reduce({%{}, [], []}, &stack_and_map/2)
|> elem(0)
|> Enum.max_by(fn {_k, v} ->
v.asleep
|> Enum.map(&Enum.sum/1)
|> Enum.sum()
end)
|> sleepiest_minute()
id * minute
end
def part2() do
{id, minute, _count} =
input()
|> Enum.map(&parse_record_pattern/1)
|> Enum.reduce({%{}, [], []}, &stack_and_map/2)
|> elem(0)
|> Enum.map(&sleepiest_minute/1)
|> Enum.max_by(fn {_id, _min, count} -> count end)
id * minute
end
defp sleepiest_minute({id, %{asleep: list_of_ranges}}) do
{minute, list} =
list_of_ranges
|> Enum.flat_map(& &1)
|> Enum.group_by(& &1)
|> Enum.max_by(fn {_k, v} -> length(v) end, fn -> {0, []} end)
{id, minute, length(list)}
end
def parse_record_pattern(string) do
<<
"[",
_date::binary-size(10),
" ",
_hour::binary-size(2),
":",
minute::binary-size(2),
"] ",
action::binary
>> = string
%{
minute: String.to_integer(minute),
action: parse_action(action)
}
end
defp parse_action("Guard #" <> string) do
[id] = Regex.run(~r/\d+/, string)
{:guard, String.to_integer(id)}
end
defp parse_action("wakes up"), do: :wake_up
defp parse_action("falls asleep"), do: :sleep
def stack_and_map(%{action: {:guard, id}}, {map, awake_stack, asleep_stack}) do
{Map.put_new(map, id, %{slept: nil, asleep: []}), [id | awake_stack], asleep_stack}
end
def stack_and_map(
%{action: :sleep, minute: minute} = _record,
{map, [current_id | awake_stack], asleep_stack}
) do
{put_in(map, [current_id, :slept], minute), awake_stack, [current_id | asleep_stack]}
end
def stack_and_map(
%{action: :wake_up, minute: minute} = _record,
{map, awake_stack, [current_id | asleep_stack]}
) do
went_to_sleep = get_in(map, [current_id, :slept])
{update_in(map, [current_id, :asleep], &[went_to_sleep..(minute - 1) | &1]),
[current_id | awake_stack], asleep_stack}
end
end
IO.puts(Day4.part1())
IO.puts(Day4.part2())
|
