add leetcode problem-cn part3

算法题（国内版）/problem (Chinese)/寻找重复的子树 [find-duplicate-subtrees].html

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+<p>给定一棵二叉树 <code>root</code>，返回所有<strong>重复的子树</strong>。</p>
+
+<p>对于同一类的重复子树，你只需要返回其中任意<strong>一棵</strong>的根结点即可。</p>
+
+<p>如果两棵树具有<strong>相同的结构</strong>和<strong>相同的结点值</strong>，则它们是<strong>重复</strong>的。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e1.jpg" style="height: 236px; width: 300px;" /></p>
+
+<pre>
+<strong>输入：</strong>root = [1,2,3,4,null,2,4,null,null,4]
+<strong>输出：</strong>[[2,4],[4]]</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e2.jpg" style="height: 125px; width: 200px;" /></p>
+
+<pre>
+<strong>输入：</strong>root = [2,1,1]
+<strong>输出：</strong>[[1]]</pre>
+
+<p><strong>示例 3：</strong></p>
+
+<p><strong><img alt="" src="https://assets.leetcode.com/uploads/2020/08/16/e33.jpg" style="height: 202px; width: 300px;" /></strong></p>
+
+<pre>
+<strong>输入：</strong>root = [2,2,2,3,null,3,null]
+<strong>输出：</strong>[[2,3],[3]]</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li>树中的结点数在<code>[1,10^4]</code>范围内。</li>
+	<li><code>-200 &lt;= Node.val &lt;= 200</code></li>
+</ul>