## Problem

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.