# 0919. Complete Binary Tree Inserter

https://leetcode.com/problems/complete-binary-tree-inserter

## Description

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:**

![](https://assets.leetcode.com/uploads/2021/08/03/lc-treeinsert.jpg)

```
**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`.

## ac

```java
```
