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43 lines
787 B
Ruby
43 lines
787 B
Ruby
START = "AAA"
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FINISH = "ZZZ"
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class Node
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attr_reader :name, :left, :right
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def initialize(name, left, right)
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@name = name
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@left = left
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@right = right
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end
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end
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raw_instructions, raw_nodes = ARGF.read.split("\n\n")
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nodes = Hash.new
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raw_nodes.each_line do |line|
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next if line.empty?
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if line =~ /^([A-Z]+) = \(([A-Z]+), ([A-Z]+)\)$/
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nodes[$1] = Node.new($1, $2, $3)
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else
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throw "unmatched line #{line}"
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end
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end
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node = nodes[START]
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instructions = raw_instructions.split("").cycle
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steps = 0
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while node.name != FINISH
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steps += 1
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instruction = instructions.next
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case instruction
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when "L"
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node = nodes[node.left]
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when "R"
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node = nodes[node.right]
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else
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throw "unexpected instruction: '#{instruction}'"
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end
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end
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puts "Part 1: #{steps}"
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