view day4b.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 9da7a71b313d
children
line wrap: on
line source

#! /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]
# Ruby arrays auto-magically grow when you set any index!
card_counts = Array.new

def add(array, index, value)
	array[index].nil? ? value : array[index] + value
end

sum = 0
File.open(file, "r").each_line(chomp: true).with_index do |line, index|
	card_counts[index] = add(card_counts, index, 1)
	card_count = card_counts[index]
	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
	if our_winning_numbers.length > 0
#		puts "Increase #{index + 1} to #{index + our_winning_numbers.length} by #{card_count}"
#		puts (1..our_winning_numbers.length)
		(1..our_winning_numbers.length).each {|v| card_counts[index + v] = add(card_counts, index + v, card_count)}
	end
end

#puts card_counts
puts card_counts.sum
puts sum