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Grokking the Coding Interview Patterns in C#

Solution: Binary Tree Cameras

Understand how to solve the binary tree camera coverage problem using dynamic programming. Learn to classify node states, apply post-order traversal, and compute minimal camera placement to cover all nodes effectively.

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Statement

You are given the root of a binary tree. Cameras can be installed on any node, and each camera can monitor itself, its parent, and its immediate children.

Your task is to determine the minimum number of cameras required to monitor every node in the tree.

Constraints:

  • The number of nodes in the tree is in the range [1,1000][1, 1000].

  • Node.data ==0== 0

Solution

Each node in the tree can be in one of three possible states, based on how it's monitored:

  • State 0 (Not covered): All the nodes below this node are monitored, but this node is not. ...