gem install binary_trees

root = [1, 2, 3, 4, 5, 6].to_root
tree = Tree.new(root)

root.val # == 1
root.left.right.val # == 5

tree.sum # == 11

tree.to_a

tree.invert # return root [1, 3, 2, nil, 6, 5, 4]