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Description

Given a binary tree, we install cameras on the nodes of the tree. 

Each camera at a node can monitor its parent, itself, and its immediate children.

Calculate the minimum number of cameras needed to monitor all nodes of the tree.

 

Example 1:

Input: [0,0,null,0,0]

Output: 1

Explanation: One camera is enough to monitor all nodes if placed as shown.

Example 2:

Input: [0,0,null,0,null,0,null,null,0]

Output: 2

Explanation: 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.


Note:

    <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>
    

Solutions

Python3

Java

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