Hash#leaf_values

class Hash
  def leaf_values
    flat_map do |k,v|
      if v.is_a?(Hash)
        v.leaf_values
      else
        [v]
      end
    end
  end
end

p({"root"=>{:a=>"tom", :b=>{:c => 1, :x => 2}}}.leaf_values) # => ["tom", 1, 2]