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55 lines
1.1 KiB
55 lines
1.1 KiB
input = ARGF.readlines(chomp: true).map(&:chars)
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# always tilts left
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def tilt(platform)
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platform
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.map {|row| row.chunk_while { [_1, _2].tally.fetch(?#, 0).even? }}
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.map {|row| row.flat_map { _1.sort.reverse }}
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end
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def load(platform)
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platform.reverse
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.each.with_index
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.sum {|row, i| row.count(?O) * (i+1) }
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end
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# part one
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p load(tilt(input.transpose).transpose)
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def spin_cycle(platform)
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return enum_for(__method__, platform) unless block_given?
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loop do
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# north
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platform = tilt(platform.transpose).transpose
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# west
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platform = tilt(platform)
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# south
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platform = tilt(platform.reverse.transpose).transpose.reverse
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# east
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platform = tilt(platform.map(&:reverse)).map(&:reverse)
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yield platform
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end
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end
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# part two
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spin = spin_cycle(input)
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seen = {}
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(1_000_000_000).times do |i|
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platform = spin.next
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if seen.has_key?(platform.hash)
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start, _ = seen.fetch(platform.hash)
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i = (1_000_000_000 - start) % (i+1 - start) + start
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p seen.find {|_,(j,_)| j == i }.fetch(1).fetch(1)
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exit
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end
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seen[platform.hash] = [i+1, load(platform)]
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end
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