Jason's plates problem

plates.rb

#!/usr/bin/env ruby

LENGTH = 5

def extend_plates(plates)
  plates.flat_map do |p|
    last = p.last
    [last - 1, last + 1].select { |d| d.between?(0, 9) }.map { |d| p + [d] }
  end
end

plates = (1..9).map { |d| [d] }
(LENGTH - 1).times { plates = extend_plates(plates) }

puts "Total: #{plates.size}"
puts "First 10: #{plates.first(10).map(&:join).join(', ')}"
puts "Sample contains 43456? #{plates.any? { |p| p.join == '43456' }}"