view day6b.rb @ 17:92144824cbb7

Add "inside the loop" counting for day 10 part 2 Use the "how many lines do we cross?" approach. We also need extra state for "am I actually inside a line, or did it just revert back on itself". Slightly slow, but not terrible.
author IBBoard <dev@ibboard.co.uk>
date Sun, 10 Dec 2023 20:26:12 +0000
parents 6e0615e54e71
children
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#! /usr/bin/env ruby

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]

time, distance = File.open(file, "r").each_line(chomp: true).map {|v| v.split(":")[1].split(" ").join("").to_i}
events = [[time, distance]]

product = events.map do |event|
	mid = (event[0].to_f / 2).floor
	first_success = (1..mid).bsearch {|i| (event[0] - i) * i > event[1]}
	num_success = (mid - first_success + 1) * 2
	event[0].odd? ? num_success : num_success - 1
end.reduce(:*)

puts product