defmodule Day05 do
def parse_integer_list(list, split) do
list
|> String.split(split, trim: true)
|> Enum.map(&String.to_integer/1)
end
def parse_data(data) do
[rules, jobs] = data
|> String.split("\n\n", trim: true)
rules = rules
|> String.split("\n", trim: true)
|> Enum.map(&parse_integer_list(&1, "|"))
|> Enum.group_by(&hd/1, &hd(tl(&1)))
|> Enum.into(%{}, fn {k, v} -> {k, MapSet.new(v)} end)
jobs = jobs
|> String.split("\n", trim: true)
|> Enum.map(&parse_integer_list(&1, ","))
{rules, jobs}
end
def part1({rules, jobs}) do
jobs
|> Enum.filter(&job_okay?(&1, rules))
|> Enum.map(&middle_page/1)
|> Enum.sum()
end
def job_okay?(job, rules) do
case job do
[] ->
true
[page | rest] ->
page_okay?(page, rest, rules) and
job_okay?(rest, rules)
end
end
def page_okay?(page, rest, rules) do
rest
|> Enum.all?(&Map.get(rules, &1, %MapSet{}) |> MapSet.member?(page) == false)
end
def middle_page(job) do
job |> Enum.at(job |> length() |> div(2))
end
def part2({rules, jobs}) do
jobs
|> Enum.reject(&job_okay?(&1, rules))
|> Enum.map(&fix_job(&1, rules))
|> Enum.map(&middle_page/1)
|> Enum.sum()
end
def fix_job(job, rules, acc \\ []) do
case job do
[] ->
Enum.reverse(acc)
job ->
{l, r} = Enum.split_with(job, &page_okay?(&1, job, rules) == false)
[next, rest] = [hd(r), l ++ tl(r)]
fix_job(rest, rules, [next | acc])
end
end
end
data = IO.read(:stdio, :eof) |> Day05.parse_data()
{time1 , ans1} = :timer.tc(fn -> Day05.part1(data) end)
IO.puts("Time : #{time1 / 1000000}")
IO.puts("Answer: #{ans1}")
{time2 , ans2} = :timer.tc(fn -> Day05.part2(data) end)
IO.puts("Time : #{time2 / 1000000}")
IO.puts("Answer: #{ans2}")
