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:

**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