binary-tree-cameras.md

<p>Given a binary tree, we install cameras on the nodes of the tree.&nbsp;</p>

<p>Each camera at&nbsp;a node can monitor <strong>its parent, itself, and its immediate children</strong>.</p>

<p>Calculate the minimum number of cameras needed to monitor all nodes of the tree.</p>

<p>&nbsp;</p>

<p><strong>Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/29/bst_cameras_01.png" style="width: 138px; height: 163px;" />
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<pre>
<strong>Input: </strong><span id="example-input-1-1">[0,0,null,0,0]</span>
<strong>Output: </strong><span id="example-output-1">1</span>
<strong>Explanation: </strong>One camera is enough to monitor all nodes if placed as shown.
</pre>

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<p><strong>Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/29/bst_cameras_02.png" style="width: 139px; height: 312px;" />
<pre>
<strong>Input: </strong><span id="example-input-2-1">[0,0,null,0,null,0,null,null,0]</span>
<strong>Output: </strong><span id="example-output-2">2
<strong>Explanation:</strong> At least two cameras are needed to monitor all nodes of the tree. The above image shows one of the valid configurations of camera placement.</span>
</pre>

<p><br />
<strong>Note:</strong></p>

<ol>
	<li>The number of nodes in the given tree will be in the range&nbsp;<code>[1, 1000]</code>.</li>
	<li><strong>Every</strong> node has value 0.</li>
</ol>
</div>
</div>