Advent Of Code - Day 16: Part 1

aoc_2020_day_16_part_one.rb

@section = File.open('input.real.txt').read.split("\n\n").compact

# Get all the rules as ranges (e.g. 0..3)
@rules = @section[0]
  .scan(/([0-9\-]+)-([0-9]+)/im)
  .collect { |start_range, end_range| (start_range.to_i..end_range.to_i) }

# Get all the numbers on the nearby tickets
@nearby_ticket_numbers = @section[2]
  .gsub("nearby tickets:\n", '')
  .gsub("\n", ',')
  .split(',')
  .compact
  .collect(&:to_i)

# Filter out the ticket numbers which aren't within any of those ranges
@nearby_ticket_error_rate = @nearby_ticket_numbers
  .select { |number| @rules.none? { |rule| rule.cover?(number) } }
  .sum

# Part one:
puts @nearby_ticket_error_rate