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