leetcode-problemset/leetcode-cn/problem (Chinese)/从上到下打印二叉树 [cong-shang-dao-xia-da-yin-er-cha-shu-lcof].html

<p>从上到下打印出二叉树的每个节点，同一层的节点按照从左到右的顺序打印。</p>

<p>&nbsp;</p>

<p>例如:<br>
给定二叉树:&nbsp;<code>[3,9,20,null,null,15,7]</code>,</p>

<pre>    3
   / \
  9  20
    /  \
   15   7
</pre>

<p>返回：</p>

<pre>[3,9,20,15,7]
</pre>

<p>&nbsp;</p>

<p><strong>提示：</strong></p>

<ol>
	<li><code>节点总数 &lt;= 1000</code></li>
</ol>