Project Notes

Binary Tree Level Order Traversal II

3 min read

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Description

tab: English
 
<p>Given the <code>root</code> of a binary tree, return <em>the bottom-up level order traversal of its nodes&#39; values</em>. (i.e., from left to right, level by level from leaf to root).</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg" style="width: 277px; height: 302px;" />
<pre>
<strong>Input:</strong> root = [3,9,20,null,null,15,7]
<strong>Output:</strong> [[15,7],[9,20],[3]]
</pre>
 
<p><strong class="example">Example 2:</strong></p>
 
<pre>
<strong>Input:</strong> root = [1]
<strong>Output:</strong> [[1]]
</pre>
 
<p><strong class="example">Example 3:</strong></p>
 
<pre>
<strong>Input:</strong> root = []
<strong>Output:</strong> []
</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 2000]</code>.</li>
	<li><code>-1000 &lt;= Node.val &lt;= 1000</code></li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/submissions/) | [solutions](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/solutions/)
 
 
tab: 中文
 
<p>给你二叉树的根节点 <code>root</code> ，返回其节点值 <strong>自底向上的层序遍历</strong> 。 （即按从叶子节点所在层到根节点所在的层，逐层从左向右遍历）</p>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg" style="width: 277px; height: 302px;" />
<pre>
<strong>输入：</strong>root = [3,9,20,null,null,15,7]
<strong>输出：</strong>[[15,7],[9,20],[3]]
</pre>
 
<p><strong>示例 2：</strong></p>
 
<pre>
<strong>输入：</strong>root = [1]
<strong>输出：</strong>[[1]]
</pre>
 
<p><strong>示例 3：</strong></p>
 
<pre>
<strong>输入：</strong>root = []
<strong>输出：</strong>[]
</pre>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li>树中节点数目在范围 <code>[0, 2000]</code> 内</li>
	<li><code>-1000 &lt;= Node.val &lt;= 1000</code></li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/binary-tree-level-order-traversal-ii/submissions/) | [题解](https://leetcode.cn/problems/binary-tree-level-order-traversal-ii/solution/)

Solutions & Notes

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