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76 lines
1.3 KiB
76 lines
1.3 KiB
require "strscan"
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def add(a, b)
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reduced("[#{a},#{b}]")
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end
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def reduced(s)
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last_s = ""
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until s == last_s
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last_s = s
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to_explode = find_nested(s)
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if to_explode
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s = explode(s, to_explode)
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next
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end
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s = s.sub(/[1-9]\d+/) {|n|
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half = n.to_i / 2.0
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pair = [half.floor, half.ceil]
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"[#{pair.join(?,)}]"
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}
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end
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s
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end
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def find_nested(s)
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ss = StringScanner.new(s)
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depth = 0
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until ss.eos?
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case
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when ss.scan(/\[/)
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if depth == 4
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a = ss.pos-1
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ss.scan(/\d+,\d+\]/)
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b = ss.pos-1
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return [a, b]
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end
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depth += 1
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when ss.scan(/\]/)
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depth -= 1
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when ss.scan(/\d+|,/)
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# no-op
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else
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fail
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end
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end
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nil
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end
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def explode(s, pair_range)
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a, b = pair_range
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pair = s[a..b].scan(/\d+/).map(&:to_i)
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[
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s[0...a].reverse.sub(/\d+/) { (_1.reverse.to_i + pair[0]).to_s.reverse }.reverse,
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0,
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s[b+1..].sub(/(\d+)/) { _1.to_i + pair[1] },
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].join
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end
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class Array
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def magnitude = 3*self[0].magnitude + 2*self[1].magnitude
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end
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class Integer
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def magnitude = self
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end
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# sum = ARGF.read.split("\n").reject(&:empty?).inject {|sum,num| add(sum, num) }
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# p eval(sum).magnitude
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p ARGF.read.split("\n").reject(&:empty?).permutation(2).map { eval(add(*_1)).magnitude }.max
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