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51 lines
1.2 KiB
51 lines
1.2 KiB
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, -1, 0]
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when ss.scan(/se/) then [ 0, -1, 1]
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when ss.scan(/sw/) then [-1, 0, 1]
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when ss.scan(/w/) then [-1, 1, 0]
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when ss.scan(/nw/) then [ 0, 1, -1]
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when ss.scan(/ne/) then [ 1, 0, -1]
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else fail
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end
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end
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deltas.inject {|(x,y,z),(dx,dy,dz)| [x+dx, y+dy, z+dz] }
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end
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tiles = Hash.new(false)
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ARGF.read.split("\n").map {|line| parse(line) }
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.each do |tile|
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tiles[tile] = !tiles[tile]
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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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candidates = tiles.keys.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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candidates.map {|coord|
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live_neighbors = NEIGHBORS.map {|n| coord.zip(n).map {|c,d| c + d }}.count {|c| tiles[c] }
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if tiles[coord]
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[coord, (1..2).cover?(live_neighbors)]
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else
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[coord, live_neighbors == 2]
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end
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}.to_h.select {|_,v| v }
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end
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100.times do
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tiles = tick(tiles)
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end
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p tiles.values.count(true)
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