Mercurial > repos > other > adventofcode2023
comparison 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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10:25dda3397797 | 11:a7fb64b48830 |
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1 #! /usr/bin/env ruby | |
2 | |
3 if ARGV.length != 1 | |
4 abort("Incorrect arguments - needs input file") | |
5 elsif not File.exist? (ARGV[0]) | |
6 abort("File #{ARGV[0]} did not exist") | |
7 end | |
8 | |
9 file = ARGV[0] | |
10 | |
11 lines = File.open(file, "r").each_line(chomp: true) | |
12 | |
13 steps = lines.first.each_char.to_a | |
14 | |
15 node_lines = lines.drop(1).to_a | |
16 | |
17 #first_node, _ = node_lines[0].split("=") | |
18 #first_node.strip! | |
19 | |
20 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 | |
21 | |
22 cur_nodes = nodes.keys.filter {|v| v[-1] == "A"} | |
23 | |
24 step_counts = cur_nodes.map do |cur_node| | |
25 step_count = 0 | |
26 step_cycle = steps.cycle | |
27 while cur_node[-1] != "Z" | |
28 step_count += 1 | |
29 cur_node = nodes[cur_node][step_cycle.next] | |
30 end | |
31 step_count | |
32 end | |
33 puts step_counts.reduce(1, :lcm) |