phone_list.rb

def consistent?(phone_numbers)
  phone_numbers.each do |num|
    phone_numbers - [ num ].each { |o| return "NO" if %r{^#{num}}.match(o) }
  end
  "YES"
end

gets.to_i.times do
  num_array = []
  gets.to_i.times { num_array << gets.chomp }
  puts consistent? num_array
end