gistfile1.rb

Node = Struct.new(:value, :left, :right)

node = Node.new(24, Node.new(12, Node.new(10), Node.new(14)), Node.new(28, nil, Node.new(30)))

def values(node)
  return [] if node.nil?
  [values(node.left),
   node.value,
   values(node.right)].flatten
end

values(node)