<p>A binary tree is <strong>uni-valued</strong> if every node in the tree has the same value.</p>

<p>Given the <code>root</code> of a binary tree, return <code>true</code><em> if the given tree is <strong>uni-valued</strong>, or </em><code>false</code><em> otherwise.</em></p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/28/unival_bst_1.png" style="width: 265px; height: 172px;" />
<pre>
<strong>Input:</strong> root = [1,1,1,1,1,null,1]
<strong>Output:</strong> true
</pre>

<p><strong>Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/28/unival_bst_2.png" style="width: 198px; height: 169px;" />
<pre>
<strong>Input:</strong> root = [2,2,2,5,2]
<strong>Output:</strong> false
</pre>

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

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 100]</code>.</li>
	<li><code>0 &lt;= Node.val &lt; 100</code></li>
</ul>