int leftHeight(Node root) {
        int h = 0;
        while (root != null) {
            root = root.left;
            h++;
        }
        return h;
    }
Date 10/06/2016
@author Tushar Roy

Given a complete binary tree, count the number of nodes.

Time complexity O(log(n) ^ 2)

Reference
https://leetcode.com/problems/count-complete-tree-nodes/
src/com/interview/tree/CountNodesCompleteTree.java