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43 lines
1.3 KiB
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43 lines
1.3 KiB
HTML
<p>给你二叉树的根结点 <code>root</code> ，请你将它展开为一个单链表：</p>
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<ul>
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<li>展开后的单链表应该同样使用 <code>TreeNode</code> ，其中 <code>right</code> 子指针指向链表中下一个结点，而左子指针始终为 <code>null</code> 。</li>
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<li>展开后的单链表应该与二叉树 <a href="https://baike.baidu.com/item/%E5%85%88%E5%BA%8F%E9%81%8D%E5%8E%86/6442839?fr=aladdin" target="_blank"><strong>先序遍历</strong></a> 顺序相同。</li>
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</ul>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/01/14/flaten.jpg" style="width: 500px; height: 226px;" />
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<pre>
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<strong>输入：</strong>root = [1,2,5,3,4,null,6]
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<strong>输出：</strong>[1,null,2,null,3,null,4,null,5,null,6]
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</pre>
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<p><strong>示例 2：</strong></p>
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<pre>
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<strong>输入：</strong>root = []
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<strong>输出：</strong>[]
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</pre>
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<p><strong>示例 3：</strong></p>
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<pre>
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<strong>输入：</strong>root = [0]
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<strong>输出：</strong>[0]
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</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul>
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<li>树中结点数在范围 <code>[0, 2000]</code> 内</li>
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<li><code>-100 <= Node.val <= 100</code></li>
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</ul>
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<p> </p>
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<p><strong>进阶：</strong>你可以使用原地算法（<code>O(1)</code> 额外空间）展开这棵树吗？</p>
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