public class CBTInserter
extends Object
919 - Complete Binary Tree Inserter\.
Medium
A **complete binary tree** is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.
Design an algorithm to insert a new node to a complete binary tree keeping it complete after the insertion.
Implement the `CBTInserter` class:
* `CBTInserter(TreeNode root)` Initializes the data structure with the `root` of the complete binary tree.
* `int insert(int v)` Inserts a `TreeNode` into the tree with value `Node.val == val` so that the tree remains complete, and returns the value of the parent of the inserted `TreeNode`.
* `TreeNode get_root()` Returns the root node of the tree.
**Example 1:**
**Input** ["CBTInserter", "insert", "insert", "get\_root"] [[[1, 2]], [3], [4], []]
**Output:** [null, 1, 2, [1, 2, 3, 4]]
**Explanation:**
CBTInserter cBTInserter = new CBTInserter([1, 2]);
cBTInserter.insert(3); // return 1
cBTInserter.insert(4); // return 2
cBTInserter.get\_root(); // return [1, 2, 3, 4]
**Constraints:**
* The number of nodes in the tree will be in the range `[1, 1000]`.
* `0 <= Node.val <= 5000`
* `root` is a complete binary tree.
* `0 <= val <= 5000`
* At most 104 calls will be made to `insert` and `get_root`.