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algorithm, image = ARGF.read.strip.split("\n\n")
algorithm = algorithm.delete("\n") # for the example
algorithm = algorithm.chars.map.with_index { [_2, _1 == ?#] }.to_h
image = image.split("\n").flat_map.with_index {|row, y|
row.chars.map.with_index {|pixel, x| [[y, x], pixel == ?#] }
}.to_h
image.default = false
def each(image)
return enum_for(__method__, image) unless block_given?
ys = image.keys.map(&:first).minmax
xs = image.keys.map(&:last).minmax
(ys[0]-1..ys[1]+1).each do |y|
(xs[0]-1..xs[1]+1).each do |x|
yield [y, x]
end
end
end
def debug(image)
ys = image.keys.map(&:first).minmax
xs = image.keys.map(&:last).minmax
puts (ys[0]-1..ys[1]+1).map {|y|
(xs[0]-1..xs[1]+1).map {|x|
image[[y,x]] ? ?# : ?.
}.join
}.join("\n")
end
50.times {
ys = image.keys.map(&:first).minmax
xs = image.keys.map(&:last).minmax
prev_default = image.default
image = each(image).to_h {|y,x|
area = (-1..1).flat_map {|dy| (-1..1).map {|dx| image[[y+dy, x+dx]] }}
index = area.map { _1 ? 1 : 0 }.join.to_i(2)
pixel = algorithm.fetch(index)
[[y,x], pixel]
}
image.default = prev_default ? algorithm.fetch(511) : algorithm.fetch(0)
}
p image.count { _2 }