public boolean isBalanced(Node root) {
        return isBalancedUtil(root) >= 0;
    }
Date 10/06/2016
@author Tushar Roy

Given a binary tree, determine if it is height-balanced.

Time complexity O(logn)

Reference
https://leetcode.com/problems/balanced-binary-tree/
src/com/interview/tree/HeightBalanced.java