<h2><a href="https://leetcode.com/problems/cousins-in-binary-tree-ii/">2641. Cousins in Binary Tree II</a></h2><h3>Medium</h3><hr><div><p>Given the <code>root</code> of a binary tree, replace the value of each node in the tree with the <strong>sum of all its cousins' values</strong>.</p>

<p>Two nodes of a binary tree are <strong>cousins</strong> if they have the same depth with different parents.</p>

<p>Return <em>the </em><code>root</code><em> of the modified tree</em>.</p>

<p><strong>Note</strong> that the depth of a node is the number of edges in the path from the root node to it.</p>

<p>&nbsp;</p>

<p><strong class="example">Example 1:</strong></p>

<img alt="" src="https://assets.leetcode.com/uploads/2023/01/11/example11.png" style="width: 571px; height: 151px;">

<pre><strong>Input:</strong> root = [5,4,9,1,10,null,7]

<strong>Output:</strong> [0,0,0,7,7,null,11]

<strong>Explanation:</strong> The diagram above shows the initial binary tree and the binary tree after changing the value of each node.

- Node with value 5 does not have any cousins so its sum is 0.

- Node with value 4 does not have any cousins so its sum is 0.

- Node with value 9 does not have any cousins so its sum is 0.

- Node with value 1 has a cousin with value 7 so its sum is 7.

- Node with value 10 has a cousin with value 7 so its sum is 7.

- Node with value 7 has cousins with values 1 and 10 so its sum is 11.

</pre>

<p><strong class="example">Example 2:</strong></p>

<img alt="" src="https://assets.leetcode.com/uploads/2023/01/11/diagram33.png" style="width: 481px; height: 91px;">

<pre><strong>Input:</strong> root = [3,1,2]

<strong>Output:</strong> [0,0,0]

<strong>Explanation:</strong> The diagram above shows the initial binary tree and the binary tree after changing the value of each node.

- Node with value 3 does not have any cousins so its sum is 0.

- Node with value 1 does not have any cousins so its sum is 0.

- Node with value 2 does not have any cousins so its sum is 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, 10⁵]</code>.</li>

<li><code>1 &lt;= Node.val &lt;= 10⁴</code></li>

</ul>

</div>