binary-tree-cameras

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Algorithms

You are given the <code>root</code> 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.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/29/bst_cameras_01.png" style="width: 138px; height: 163px;" />
<pre>
Input: root = [0,0,null,0,0]
Output: 1
Explanation: One camera is enough to monitor all nodes if placed as shown.
</pre>

Example 2:
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/29/bst_cameras_02.png" style="width: 139px; height: 312px;" />
<pre>
Input: root = [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.
</pre>

&nbsp;
Constraints:

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 1000]</code>.</li>
	<li><code>Node.val == 0</code></li>
</ul>

minCameraCover

Binary Tree Cameras

Distribute Coins in Binary Tree

distribute-coins-in-binary-tree

在二叉树中分配硬币

Choose Edges to Maximize Score in a Tree

choose-edges-to-maximize-score-in-a-tree

选择边来最大化树的得分

Tree

Depth-First Search

Dynamic Programming

Binary Tree

给定一个二叉树，我们在树的节点上安装摄像头。

节点上的每个摄影头都可以监视其父对象、自身及其直接子对象。

计算监控树的所有节点所需的最小摄像头数量。

&nbsp;

示例 1：

<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/bst_cameras_01.png" style="height: 163px; width: 138px;">

<pre>输入：[0,0,null,0,0]
输出：1
解释：如图所示，一台摄像头足以监控所有节点。
</pre>

示例 2：

<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/bst_cameras_02.png" style="height: 312px; width: 139px;">

<pre>输入：[0,0,null,0,null,0,null,null,0]
输出：2
解释：需要至少两个摄像头来监视树的所有节点。 上图显示了摄像头放置的有效位置之一。
</pre>

 
提示：

<ol>
	<li>给定树的节点数的范围是&nbsp;<code>[1, 1000]</code>。</li>
	<li>每个节点的值都是 0。</li>
</ol>