AdventOfCode/2020/elixir/day16/day16part1.exs

42 lines
1 KiB
Elixir
Raw Normal View History

defmodule Day16Part1 do
def run do
2020-12-16 14:57:57 +00:00
{rules, tickets} = File.read!("input") |> parse_input()
2020-12-16 14:57:57 +00:00
Enum.flat_map(tickets, &find_invalid_fields(&1, rules))
|> Enum.sum()
|> IO.puts()
end
2020-12-16 14:57:57 +00:00
def find_invalid_fields(ticket, rules) do
Enum.reject(ticket, fn field ->
Enum.any?(rules, fn {_name, range1, range2} -> field in range1 || field in range2 end)
end)
end
def parse_input(input) do
2020-12-16 14:57:57 +00:00
[rules, _, [_ | nearby_tickets]] =
input
|> String.split("\n\n", trim: true)
|> Enum.map(&String.split(&1, "\n", trim: true))
rules = Enum.map(rules, &parse_rule/1)
2020-12-16 14:57:57 +00:00
nearby_tickets =
for ticket <- nearby_tickets do
ticket |> String.split(",") |> Enum.map(&String.to_integer/1)
end
2020-12-16 14:57:57 +00:00
{rules, nearby_tickets}
end
def parse_rule(rule) do
[name | ranges] =
Regex.run(~r/\A(.*): (\d+)-(\d+) or (\d+)-(\d+)\z/, rule, capture: :all_but_first)
[a, b, c, d] = Enum.map(ranges, &String.to_integer/1)
{name, a..b, c..d}
end
end
Day16Part1.run()