12_connected_groups.rb

require_relative 'lib/search'

neighbours = ARGF.each_line.to_h { |l|
  left, right = l.split('<->')
  [Integer(left), right.split(?,).map(&method(:Integer))]
}

puts 0.step { |i|
  break i if neighbours.empty?

  _, _, seen = Search::bfs(neighbours.keys.first, neighbours, ->(_) { false })

  puts seen.size if seen.include?(0)

  neighbours.delete_if { |k, _| seen.include?(k) }
}