Insert Node in a Binary Search Tree(lintcode 85)

Description

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.

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

Example

Given binary search tree as follow, after Insert node 6, the tree should be:

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

Interface

/**
 * 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
    }
}

Solution

/**
 * 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 tmp = root;
        TreeNode last = null;

        while (tmp != null) {
            last = tmp;
            if (tmp.val > node.val) {
                tmp = tmp.left;
            } else {
                tmp = tmp.right;
            }
        }

        if (last.val > node.val) {
            last.left = node;
        } else {
            last.right = node;
        }

        return root;
    }
}