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51 lines
1.4 KiB
51 lines
1.4 KiB
cubes = ARGF.read.lines(chomp: true).map { _1.split(?,).map(&:to_i) }
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# part one
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# p cubes.sum {|cube|
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# 6 - cubes.count {|other|
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# cube.zip(other).map { _1 - _2 }.map(&:abs).sum == 1
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# }
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# }
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deltas = [
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[-1, 0, 0],
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[ 1, 0, 0],
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[ 0, -1, 0],
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[ 0, 1, 0],
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[ 0, 0, -1],
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[ 0, 0, 1],
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]
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bounds = cubes.transpose.map(&:minmax).map {|(min, max)| (min-1..max+1) }
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cubes = cubes.to_h { [_1, true] }
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corners = [
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[bounds[0].begin, bounds[1].begin, bounds[2].begin],
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[bounds[0].begin, bounds[1].begin, bounds[2].end],
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[bounds[0].begin, bounds[1].end, bounds[2].begin],
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[bounds[0].begin, bounds[1].end, bounds[2].end],
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[bounds[0].end, bounds[1].begin, bounds[2].begin],
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[bounds[0].end, bounds[1].begin, bounds[2].end],
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[bounds[0].end, bounds[1].end, bounds[2].begin],
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[bounds[0].end, bounds[1].end, bounds[2].end],
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]
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frontier = [corners[0]]
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seen = Hash.new
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until frontier.empty?
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current = frontier.shift
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neighbors = deltas.map {|delta| current.zip(delta).map { _1 + _2 }}
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.select {|neighbor| bounds.zip(neighbor).all? {|(bound, i)| bound.cover?(i) }}
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seen[current] = neighbors.any? { cubes.has_key?(_1) }
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frontier.concat(neighbors.reject {|neighbor| seen.has_key?(neighbor) || cubes.has_key?(neighbor) })
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frontier.uniq!
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end
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p cubes.keys.sum {|cube|
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neighbors = deltas.map {|delta| cube.zip(delta).map { _1 + _2 }}
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neighbors.count { seen.has_key?(_1) }
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}
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