Sum of all right leaf nodes of binary tree in ruby

Ruby program for Sum of all right leaf nodes of binary tree. Here mentioned other language solution.

#    Ruby program for
#    Sum of all right leaves nodes in a binary tree
#    Using recursion

#  Binary Tree node
class TreeNode 
	# Define the accessor and reader of class TreeNode
	attr_reader :data, :left, :right
	attr_accessor :data, :left, :right
	def initialize(data) 
		#  Set node value
		self.data = data
		self.left = nil
		self.right = nil
	end
end

class BinaryTree 
	# Define the accessor and reader of class BinaryTree
	attr_reader :root
	attr_accessor :root
	def initialize() 
		self.root = nil
	end

	#  Display pre order elements
	def preorder(node) 
		if (node != nil) 
			#  Print node value
			print("  ", node.data)
			self.preorder(node.left)
			self.preorder(node.right)
		end

	end

	#  Returns the Sum of all the right leaves in binary tree
	def rightLeavesSum(node) 
		sum = 0
		if (node != nil) 
			if (node.right != nil && 
                node.right.left == nil && 
                node.right.right == nil) 
				#  When get right leaf node
				sum = node.right.data
			end

			#  Recursively visit left and right subtree.
			#  And find sum of right leaf nodes
			sum = sum + self.rightLeavesSum(node.left) + 
              self.rightLeavesSum(node.right)
		end
		return sum
	end
end

def main() 
	#  New binary tree
	tree = BinaryTree.new()
	#    Constructor binary tree
	#    -----------------------
	#          6
	#         / \ 
	#        /   \                             
	#       /     \    
	#      2       3     
	#     / \       \               
	#    8   10      1
	#       /  \    / \
	#      6   -2  4   5
	#  Add tree node
	tree.root = TreeNode.new(6)
	tree.root.left = TreeNode.new(2)
	tree.root.left.left = TreeNode.new(8)
	tree.root.left.right = TreeNode.new(10)
	tree.root.left.right.right = TreeNode.new(-2)
	tree.root.left.right.left = TreeNode.new(6)
	tree.root.right = TreeNode.new(3)
	tree.root.right.right = TreeNode.new(1)
	tree.root.right.right.left = TreeNode.new(4)
	tree.root.right.right.right = TreeNode.new(5)
	print("\n Tree Nodes : ")
	tree.preorder(tree.root)
	#  Find right leaf sum
	sum = tree.rightLeavesSum(tree.root)
	#  Display result
	print("\n Right leaves nodes sum : ", sum)
end

main()

Output

 Tree Nodes :   6  2  8  10  6  -2  3  1  4  5
 Right leaves nodes sum : 3