public int closestValue(Node root, double target) {
        int r = target > 0 ? Integer.MIN_VALUE : Integer.MAX_VALUE;
        return closestValueUtil(root, target, r);
    }
Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target.
https://leetcode.com/problems/closest-binary-search-tree-value/
src/com/interview/tree/ClosestValueBinaryTree.java