I Problem
You are given the root
of a binary tree. We install cameras on the tree nodes where each camera at a node can monitor its parent, itself, and its immediate children.
Return the minimum number of cameras needed to monitor all nodes of the tree.
Example 1
Input: root = [0, 0, null, 0, 0]
Output: 1
Explanation: One camera is enough to monitor all nodes if placed as shown.