univalued-binary-tree

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Algorithms

A binary tree is uni-valued if every node in the tree has the same value.

Given the <code>root</code> of a binary tree, return <code>true</code> if the given tree is uni-valued, or <code>false</code> otherwise.

&nbsp;
Example 1:
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/28/unival_bst_1.png" style="width: 265px; height: 172px;" />
<pre>
Input: root = [1,1,1,1,1,null,1]
Output: true
</pre>

Example 2:
<img alt="" src="https://assets.leetcode.com/uploads/2018/12/28/unival_bst_2.png" style="width: 198px; height: 169px;" />
<pre>
Input: root = [2,2,2,5,2]
Output: false
</pre>

&nbsp;
Constraints:

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 100]</code>.</li>
	<li><code>0 &lt;= Node.val &lt; 100</code></li>
</ul>

第 117 场周赛

weekly-contest-117

isUnivalTree

Univalued Binary Tree

Find All The Lonely Nodes

find-all-the-lonely-nodes

寻找所有的独生节点

Tree

Depth-First Search

Breadth-First Search

Binary Tree

如果二叉树每个节点都具有相同的值，那么该二叉树就是单值二叉树。

只有给定的树是单值二叉树时，才返回&nbsp;<code>true</code>；否则返回 <code>false</code>。

&nbsp;

示例 1：

<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/screen-shot-2018-12-25-at-50104-pm.png" style="height: 159px; width: 200px;">

<pre>输入：[1,1,1,1,1,null,1]
输出：true
</pre>

示例 2：

<img alt="" src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2018/12/29/screen-shot-2018-12-25-at-50050-pm.png" style="height: 158px; width: 200px;">

<pre>输入：[2,2,2,5,2]
输出：false
</pre>

&nbsp;

提示：

<ol>
	<li>给定树的节点数范围是&nbsp;<code>[1, 100]</code>。</li>
	<li>每个节点的值都是整数，范围为&nbsp;<code>[0, 99]</code>&nbsp;。</li>
</ol>