Mercurial > repos > other > adventofcode2023
view day8b.rb @ 11:a7fb64b48830
Implement Day 8 - node/map walking
Cheated on part 2 by finding out that the routes loop
and you need to do the lowest-common-multiple to get a VERY
large number
author | IBBoard <dev@ibboard.co.uk> |
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date | Sat, 09 Dec 2023 16:37:20 +0000 |
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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] lines = File.open(file, "r").each_line(chomp: true) steps = lines.first.each_char.to_a node_lines = lines.drop(1).to_a #first_node, _ = node_lines[0].split("=") #first_node.strip! nodes = node_lines.map {|line| node, rest = line.split("="); left, right = rest.split(","); [node.strip, {"L" => left.strip[1..-1], "R" => right.strip[0..-2]}]}.to_h cur_nodes = nodes.keys.filter {|v| v[-1] == "A"} step_counts = cur_nodes.map do |cur_node| step_count = 0 step_cycle = steps.cycle while cur_node[-1] != "Z" step_count += 1 cur_node = nodes[cur_node][step_cycle.next] end step_count end puts step_counts.reduce(1, :lcm)