LC 968 Binary Tree Cameras | Greedy + DFS HARD | Explained

Welcome to *Day 16* of the *75 Hard DSA* Challenge

In this video, I solve and explain *LeetCode 968 – Binary Tree Cameras,* a classic HARD *greedy + DFS* problem where we must place the minimum number of cameras to monitor every node in a binary tree.

*What you’ll learn in this video:*
* Why greedy placement works on trees
* Understanding node states (covered / uncovered / camera)
* How postorder DFS helps make optimal decisions
* When and where to place cameras
* Handling the root node edge case
* Writing a clean recursive solution

*Key Concept:*
This problem is solved using a postorder DFS with *state tracking.*

Each node returns one of three states:
* 0 → Not covered
* 1 → Covered (no camera)
* 2 → Has camera

*Rules:*
* If any child is uncovered → place camera
* If any child has camera → node is covered
* Otherwise → node is uncovered
* At the end, we check the root and place a camera if needed.

This greedy DFS guarantees the minimum number of cameras.

*75 Hard sheet:* https://docs.google.com/spreadsheets/d/1kwYkCE0F1S6Jsl12pwxhrg2mTcJHMasfo1Ep3-47qbI/edit?usp=sharing
*Problem Link:* https://leetcode.com/problems/binary-tree-cameras
*Solution Link:* https://github.com/sibasundarj8/75-Hard-DSA-Challenge/blob/main/src/Day_16_LC_968.java

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