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2471-minimum-number-of-operations-to-sort-a-binary-tree-by-level/README.md

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+<h2><a href="https://leetcode.com/problems/minimum-number-of-operations-to-sort-a-binary-tree-by-level/">2471. Minimum Number of Operations to Sort a Binary Tree by Level</a></h2><h3>Medium</h3><hr><div><p>You are given the <code>root</code> of a binary tree with <strong>unique values</strong>.</p>
+
+<p>In one operation, you can choose any two nodes <strong>at the same level</strong> and swap their values.</p>
+
+<p>Return <em>the minimum number of operations needed to make the values at each level sorted in a <strong>strictly increasing order</strong></em>.</p>
+
+<p>The <strong>level</strong> of a node is the number of edges along the path between it and the root node<em>.</em></p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/09/18/image-20220918174006-2.png" style="width: 500px; height: 324px;">
+<pre><strong>Input:</strong> root = [1,4,3,7,6,8,5,null,null,null,null,9,null,10]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong>
+- Swap 4 and 3. The 2<sup>nd</sup> level becomes [3,4].
+- Swap 7 and 5. The 3<sup>rd</sup> level becomes [5,6,8,7].
+- Swap 8 and 7. The 3<sup>rd</sup> level becomes [5,6,7,8].
+We used 3 operations so return 3.
+It can be proven that 3 is the minimum number of operations needed.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/09/18/image-20220918174026-3.png" style="width: 400px; height: 303px;">
+<pre><strong>Input:</strong> root = [1,3,2,7,6,5,4]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong>
+- Swap 3 and 2. The 2<sup>nd</sup> level becomes [2,3].
+- Swap 7 and 4. The 3<sup>rd</sup> level becomes [4,6,5,7].
+- Swap 6 and 5. The 3<sup>rd</sup> level becomes [4,5,6,7].
+We used 3 operations so return 3.
+It can be proven that 3 is the minimum number of operations needed.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/09/18/image-20220918174052-4.png" style="width: 400px; height: 274px;">
+<pre><strong>Input:</strong> root = [1,2,3,4,5,6]
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> Each level is already sorted in increasing order so return 0.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the tree is in the range <code>[1, 10<sup>5</sup>]</code>.</li>
+	<li><code>1 &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
+	<li>All the values of the tree are <strong>unique</strong>.</li>
+</ul>
+</div>