leetcode-problemset/leetcode/problem/complete-binary-tree-inserter.html

<p>A <strong>complete binary tree</strong> is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.</p>

<p>Design an algorithm to insert a new node to a complete binary tree keeping it complete after the insertion.</p>

<p>Implement the <code>CBTInserter</code> class:</p>

<ul>
	<li><code>CBTInserter(TreeNode root)</code> Initializes the data structure with the <code>root</code> of the complete binary tree.</li>
	<li><code>int insert(int v)</code> Inserts a <code>TreeNode</code> into the tree with value <code>Node.val == val</code> so that the tree remains complete, and returns the value of the parent of the inserted <code>TreeNode</code>.</li>
	<li><code>TreeNode get_root()</code> Returns the root node of the tree.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/08/03/lc-treeinsert.jpg" style="width: 500px; height: 143px;" />
<pre>
<strong>Input</strong>
[&quot;CBTInserter&quot;, &quot;insert&quot;, &quot;insert&quot;, &quot;get_root&quot;]
[[[1, 2]], [3], [4], []]
<strong>Output</strong>
[null, 1, 2, [1, 2, 3, 4]]

<strong>Explanation</strong>
CBTInserter cBTInserter = new CBTInserter([1, 2]);
cBTInserter.insert(3);  // return 1
cBTInserter.insert(4);  // return 2
cBTInserter.get_root(); // return [1, 2, 3, 4]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree will be in the range <code>[1, 1000]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 5000</code></li>
	<li><code>root</code> is a complete binary tree.</li>
	<li><code>0 &lt;= val &lt;= 5000</code></li>
	<li>At most <code>10<sup>4</sup></code> calls will be made to <code>insert</code> and <code>get_root</code>.</li>
</ul>