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Grokking the Coding Interview Patterns

Solution: Binary Tree Cameras

Explore how to use dynamic programming to determine the least number of cameras required to cover every node in a binary tree. Understand the three coverage states and apply a recursive post-order traversal to optimize camera placement. This lesson equips you with a methodical approach to solve complex tree monitoring problems efficiently.

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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 ...