Lintcode Insert Node in a Binary Search Tree

Given a binary search tree and a new tree node, insert the node into the tree. You should keep the tree still be a valid binary search tree.

Example

Example 1:
 Input:  tree = {}, node = 1
 Output:  1
 
 Explanation:
 Insert node 1 into the empty tree, so there is only one node on the tree.

Example 2:
 Input: tree = {2,1,4,3}, node = 6
 Output: {2,1,4,3,6}
 
 Explanation: 
 Like this:



   2             2
  / \           / \
 1   4   -->   1   4
    /             / \ 
   3             3   6
  

Challenge

Can you do it without recursion?

Notice

You can assume there is no duplicate values in this tree + node.

Code (Java):

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */


public class Solution {
    /*
     * @param root: The root of the binary search tree.
     * @param node: insert this node into the binary search tree
     * @return: The root of the new binary search tree.
     */
    public TreeNode insertNode(TreeNode root, TreeNode node) {
        // write your code here
        if (root == null) {
            return node;
        }
        
        TreeNode p = root;
        TreeNode parent  = null;
        
        while (p != null) {
            if (p.val < node.val) {
                parent = p;
                p = p.right;
            } else {
                parent = p;
                p = p.left;
            }
        }
        
        if (parent.val < node.val) {
            parent.right = node;
        } else {
            parent.left = node;
        }
        
        return root;
    }
}