> For the complete documentation index, see [llms.txt](https://code-snippets.hbamithkumara.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://code-snippets.hbamithkumara.com/leetcode/problems/901-1000/binary-tree-cameras.md).
# 968. Binary Tree Cameras
### Description
Given a binary tree, we install cameras on the nodes of the tree.
Each camera at a node can monitor **its parent, itself, and its immediate children**.
Calculate the minimum number of cameras needed to monitor all nodes of the tree.
### Constraints
1. The number of nodes in the given tree will be in the range `[1, 1000]`.
2. **Every** node has value 0.
### Approach
### Links
* GeeksforGeeks
* Leetcode
* ProgramCreek
* YouTube
### **Examples**
{% tabs %}
{% tab title="Example 1" %}
**Input:** \[0, 0, null, 0, 0]
**Output:** 1
**Explanation:** One camera is enough to monitor all nodes if placed as shown.
{% endtab %}
{% tab title="Example 2" %}
**Input:** \[0, 0, null, 0, null, 0, null, null, 0]
**Output:** 2
**Explanation:** At least two cameras are needed to monitor all nodes of the tree. The above image shows one of the valid configurations of camera placement.
{% endtab %}
{% endtabs %}
### **Solutions**
{% tabs %}
{% tab title="TreeNode" %}
```java
// Definition for a binary tree node.
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode() {}
TreeNode(int val) {
this.val = val;
}
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
```
{% endtab %}
{% tab title="Solution 1" %}
```java
/**
* Time complexity :
* Space complexity :
*/
class Solution {
private int count = 0;
public int minCameraCover(TreeNode root) {
return dfs(root) > 2? count + 1: count;
}
private int dfs(TreeNode node) {
if(node == null) {
return 0;
}
int val = dfs(node.left) + dfs(node.right);
if(val == 0) {
return 3;
}
if(val < 3) {
return 0;
}
count++;
return 1;
}
}
```
{% endtab %}
{% endtabs %}
### **Follow up**
*
