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Problem 18: Security Network (Cameras)

Problem Statement

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.

Input Format

  • The root of a binary tree.

Example

Input: root = [0, 0, null, 0, 0]
Output: 1