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56 lines
1.2 KiB
56 lines
1.2 KiB
require "set"
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require "strscan"
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def parse(line)
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deltas = []
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ss = StringScanner.new(line)
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until ss.eos?
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deltas << case
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when ss.scan(/e/) then [ 1, 0]
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when ss.scan(/se/) then [ 0, 1]
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when ss.scan(/sw/) then [-1, 1]
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when ss.scan(/w/) then [-1, 0]
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when ss.scan(/nw/) then [ 0, -1]
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when ss.scan(/ne/) then [ 1, -1]
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else fail
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end
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end
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deltas.inject {|c,d| c.zip(d).map {|c,d| c+d }}
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end
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NEIGHBORS = %w[ e se sw w nw ne ].map {|dir| parse(dir) }
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def tick(tiles)
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coords = Set.new(tiles.flat_map {|coord|
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[
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coord,
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*NEIGHBORS.map {|n| coord.zip(n).map {|c,d| c+d }},
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]
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})
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Set.new(coords.select {|coord|
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live_neighbors = NEIGHBORS.map {|n| coord.zip(n).map {|c,d| c+d }}.count {|c| tiles.include?(c) }
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if tiles.include?(coord)
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(1..2).cover?(live_neighbors)
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else
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live_neighbors == 2
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end
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})
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end
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tiles = Set.new
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ARGF.read.split("\n").each do |line|
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tile = parse(line)
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if tiles.include?(tile)
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tiles.delete(tile)
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else
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tiles << tile
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end
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end
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100.times do |i|
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tiles = tick(tiles)
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end
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p tiles.size
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