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.
30:00
Java
Binary Tree Cameras
hard
Topics
Companies
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
Constraints:
The number of nodes is in the range [1,1000].
Node.val==0
Input
arr ={"root":[0,0,null,0,0]}
4 nodes. A camera watches itself, its parent and its children. Work bottom up so no camera is wasted.