view day4.rb @ 24:19481b061461

Implement tilting and cycling for Day 14 part 2 Lots of false starts trying to iterate. Eventually looked for "back in same position" to spot a loop. Then took longer to spot that "same position" isn't necessarily "start position" and loop can be offset!
author IBBoard <dev@ibboard.co.uk>
date Sat, 16 Dec 2023 20:39:02 +0000
parents 9da7a71b313d
children
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#! /usr/bin/env ruby

require 'set'

if ARGV.length != 1
        abort("Incorrect arguments - needs input file")
elsif not File.exist? (ARGV[0])
	abort("File #{ARGV[0]} did not exist")
end

file = ARGV[0]

sum = 0
File.open(file, "r").each_line(chomp: true) do |line|
	winning_number_str, our_number_str = line.split(":")[1].split("|").map(&:chomp)
	winning_numbers = Set.new(winning_number_str.split(" ").map(&:to_i))
	our_numbers = Set.new(our_number_str.split(" ").map(&:to_i))
	our_winning_numbers = winning_numbers & our_numbers
	sum += our_winning_numbers.length > 0 ? 2 ** (our_winning_numbers.length - 1) : 0
end

puts sum