In a binary tree, the balance ratio of node v, bal(v), is the number of nodes in the left subtree of node v divided by the sum of the number of nodes in the right and left subtrees of node v. bal(a leaf node) = . A tree T is said to be -balanced if, for all nodes v in T, - < bal(v) < + .

Design an efficient recursive algorithm that determines whether a binary tree is -balanced. What is the time complexity of your algorithm?