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| defmodule Day4 do
defmodule State do
defstruct [:guard_id, :start, :sleep]
end
defp desc_minutes({_k, ranges}) do
ranges
|> Enum.reduce(0, fn x, sum ->
sum + Enum.count(x)
end)
|> Kernel.*(-1)
end
def find_sleep_constant(spec) do
{guard, sleep_durations} =
spec
|> parse
|> Enum.sort_by(&desc_minutes/1)
|> hd
guard * most_sleepy_minute(sleep_durations)
end
def sleepiest_guard_minute(spec) do
{guard_id, {min, _count}} =
spec
|> parse
|> Enum.map(fn {guard_id, durations} ->
{min, occurences} =
durations
|> Enum.flat_map(&Enum.to_list/1)
|> Enum.group_by(& &1)
|> Enum.max_by(fn {_min, occurences} -> Enum.count(occurences) end)
{guard_id, {min, length(occurences)}}
end)
|> Enum.max_by(fn {_guard_id, {_min, count}} -> count end)
{guard_id, min}
end
def most_sleepy_minute(sleep_durations) do
{minute, _} =
sleep_durations
|> Enum.flat_map(&Enum.to_list/1)
|> Enum.group_by(& &1)
|> Enum.sort_by(fn {_k, v} -> -1 * Enum.count(v) end)
|> hd
minute
end
def parse(spec) do
{_state, logs} =
spec
|> String.split("\n", trim: true)
|> Enum.sort()
|> Enum.map(&parse_line/1)
|> Enum.reduce({_state = %State{}, _out = %{}}, fn x, {state, out} ->
case x do
{:start, guard_id, _minutes} ->
{%{state | guard_id: guard_id}, out}
{:sleep, minutes} ->
{%{state | start: minutes}, out}
{:wake, minutes} ->
prev_sleep = out[state.guard_id] || []
{state, Map.put(out, state.guard_id, [state.start..(minutes - 1) | prev_sleep])}
end
end)
logs
end
def parse_line(line) do
<<"[", _year::32, "-", _month::16, "-", _day::16, " ", _hour::16, ":",
minutes_bin::binary-size(2), "] ", note::binary>> = line
parse_note(note, String.to_integer(minutes_bin))
end
def parse_note("wakes up", minutes) do
{:wake, minutes}
end
def parse_note("falls asleep", minutes) do
{:sleep, minutes}
end
def parse_note(begin_note, minutes) do
guard_id =
Regex.named_captures(~r[Guard #(?<guard_id>\d+) begins shift], begin_note)
|> Map.get("guard_id")
|> String.to_integer()
{:start, guard_id, minutes}
end
end
defmodule Day4Test do
use ExUnit.Case
import Day4
test "parses the times when each guard sleeps" do
assert parse("""
[1518-11-01 00:00] Guard #10 begins shift
[1518-11-01 00:05] falls asleep
[1518-11-01 00:25] wakes up
[1518-11-01 00:30] falls asleep
[1518-11-01 00:55] wakes up
[1518-11-01 23:58] Guard #99 begins shift
[1518-11-02 00:40] falls asleep
[1518-11-02 00:50] wakes up
[1518-11-03 00:05] Guard #10 begins shift
[1518-11-03 00:24] falls asleep
[1518-11-03 00:29] wakes up
[1518-11-04 00:02] Guard #99 begins shift
[1518-11-04 00:36] falls asleep
[1518-11-04 00:46] wakes up
[1518-11-05 00:03] Guard #99 begins shift
[1518-11-05 00:45] falls asleep
[1518-11-05 00:55] wakes up
[1518-11-08 00:03] Guard #99334 begins shift
[1518-11-08 00:45] falls asleep
[1518-11-08 00:55] wakes up
""") == %{
10 => [5..24, 30..54, 24..28] |> Enum.reverse(),
99 => [40..49, 36..45, 45..54] |> Enum.reverse(),
99334 => [45..54]
}
end
test "find_sleep_constant" do
assert find_sleep_constant("""
[1518-11-01 00:00] Guard #10 begins shift
[1518-11-01 00:05] falls asleep
[1518-11-01 00:25] wakes up
[1518-11-01 00:30] falls asleep
[1518-11-01 00:55] wakes up
[1518-11-01 23:58] Guard #99 begins shift
[1518-11-02 00:40] falls asleep
[1518-11-02 00:50] wakes up
[1518-11-03 00:05] Guard #10 begins shift
[1518-11-03 00:24] falls asleep
[1518-11-03 00:29] wakes up
[1518-11-04 00:02] Guard #99 begins shift
[1518-11-04 00:36] falls asleep
[1518-11-04 00:46] wakes up
[1518-11-05 00:03] Guard #99 begins shift
[1518-11-05 00:45] falls asleep
[1518-11-05 00:55] wakes up
""") == 240
end
test "parses line" do
assert parse_line("[1518-11-01 00:08] wakes up") == {:wake, 8}
assert parse_line("[1518-11-01 00:30] falls asleep") == {:sleep, 30}
assert parse_line("[1518-11-01 00:23] Guard #10 begins shift") == {:start, 10, 23}
assert parse_line("[1518-11-01 00:23] Guard #99 begins shift") == {:start, 99, 23}
end
test "file" do
assert 240 ==
find_sleep_constant("""
[1518-11-01 00:00] Guard #10 begins shift
[1518-11-01 00:05] falls asleep
[1518-11-01 00:25] wakes up
[1518-11-01 00:30] falls asleep
[1518-11-01 00:55] wakes up
[1518-11-01 23:58] Guard #99 begins shift
[1518-11-02 00:40] falls asleep
[1518-11-02 00:50] wakes up
[1518-11-03 00:05] Guard #10 begins shift
[1518-11-03 00:24] falls asleep
[1518-11-03 00:29] wakes up
[1518-11-04 00:02] Guard #99 begins shift
[1518-11-04 00:36] falls asleep
[1518-11-04 00:46] wakes up
[1518-11-05 00:03] Guard #99 begins shift
[1518-11-05 00:45] falls asleep
[1518-11-05 00:55] wakes up
""")
assert File.read!("./input.txt")
|> find_sleep_constant == 30630
end
test "sleepiest_guard_minute" do
assert {99, 45} ==
sleepiest_guard_minute("""
[1518-11-01 00:00] Guard #10 begins shift
[1518-11-01 00:05] falls asleep
[1518-11-01 00:25] wakes up
[1518-11-01 00:30] falls asleep
[1518-11-01 00:55] wakes up
[1518-11-01 23:58] Guard #99 begins shift
[1518-11-02 00:40] falls asleep
[1518-11-02 00:50] wakes up
[1518-11-03 00:05] Guard #10 begins shift
[1518-11-03 00:24] falls asleep
[1518-11-03 00:29] wakes up
[1518-11-04 00:02] Guard #99 begins shift
[1518-11-04 00:36] falls asleep
[1518-11-04 00:46] wakes up
[1518-11-05 00:03] Guard #99 begins shift
[1518-11-05 00:45] falls asleep
[1518-11-05 00:55] wakes up
""")
assert {guard, min} =
File.read!("./input.txt")
|> sleepiest_guard_minute
assert guard * min == 99
end
end
|