view day2b.rb @ 39:0e17e4bd97a9 default tip

Rewrite as four-dimensional route finding The grid isn't just a 2D grid. The constraints make it 4D: * X * Y * Last direction * Number of steps in that direction By tracking all four dimensions, we can find the shortest route for _all_ combinations of the constraint. Previously, we were dropping routes that were currently longer but ended up shorter because they could take subsequent steps that other routes couldn't.
author IBBoard <dev@ibboard.co.uk>
date Sun, 22 Sep 2024 11:30:53 +0100
parents 49dd1ae93696
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]

sum = 0
File.open(file, "r").each_line do |line|
	_, all_picks = line.split(":")
	sum += all_picks.split(";").map do |pick|
		pick.split(",").to_h { |colour_pick| colour_pick.strip.split(" ").reverse }.transform_values(&:to_i)
	end.reduce(Hash.new) {|reduced,obj| reduced.merge(obj) { |key,val1,val2| val1 > val2 ? val1 : val2 }}.values.reduce(1, :*)
end

puts sum