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Description
tab: English
<p>Given the <code>root</code> of a binary search tree, and an integer <code>k</code>, return <em>the</em> <code>k<sup>th</sup></code> <em>smallest value (<strong>1-indexed</strong>) of all the values of the nodes in the tree</em>.</p>
<p> </p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree1.jpg" style="width: 212px; height: 301px;" />
<pre>
<strong>Input:</strong> root = [3,1,4,null,2], k = 1
<strong>Output:</strong> 1
</pre>
<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree2.jpg" style="width: 382px; height: 302px;" />
<pre>
<strong>Input:</strong> root = [5,3,6,2,4,null,null,1], k = 3
<strong>Output:</strong> 3
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li>The number of nodes in the tree is <code>n</code>.</li>
<li><code>1 <= k <= n <= 10<sup>4</sup></code></li>
<li><code>0 <= Node.val <= 10<sup>4</sup></code></li>
</ul>
<p> </p>
<p><strong>Follow up:</strong> If the BST is modified often (i.e., we can do insert and delete operations) and you need to find the kth smallest frequently, how would you optimize?</p>
> [!tip]- Hint 1
>
> Try to utilize the property of a BST.
> [!tip]- Hint 2
>
> Try in-order traversal. (Credits to @chan13)
> [!tip]- Hint 3
>
> What if you could modify the BST node's structure?
> [!tip]- Hint 4
>
> The optimal runtime complexity is O(height of BST).
---
[submissions](https://leetcode.com/problems/kth-smallest-element-in-a-bst/submissions/) | [solutions](https://leetcode.com/problems/kth-smallest-element-in-a-bst/solutions/)
tab: 中文
<p>给定一个二叉搜索树的根节点 <code>root</code> ，和一个整数 <code>k</code> ，请你设计一个算法查找其中第 <code>k</code><strong> </strong>小的元素（从 1 开始计数）。</p>
<p> </p>
<p><strong>示例 1：</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree1.jpg" style="width: 212px; height: 301px;" />
<pre>
<strong>输入：</strong>root = [3,1,4,null,2], k = 1
<strong>输出：</strong>1
</pre>
<p><strong>示例 2：</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree2.jpg" style="width: 382px; height: 302px;" />
<pre>
<strong>输入：</strong>root = [5,3,6,2,4,null,null,1], k = 3
<strong>输出：</strong>3
</pre>
<p> </p>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li>树中的节点数为 <code>n</code> 。</li>
<li><code>1 <= k <= n <= 10<sup>4</sup></code></li>
<li><code>0 <= Node.val <= 10<sup>4</sup></code></li>
</ul>
<p> </p>
<p><strong>进阶：</strong>如果二叉搜索树经常被修改（插入/删除操作）并且你需要频繁地查找第 <code>k</code> 小的值，你将如何优化算法？</p>
> [!tip]- 提示 1
>
> Try to utilize the property of a BST.
> [!tip]- 提示 2
>
> Try in-order traversal. (Credits to @chan13)
> [!tip]- 提示 3
>
> What if you could modify the BST node's structure?
> [!tip]- 提示 4
>
> The optimal runtime complexity is O(height of BST).
---
[提交记录](https://leetcode.cn/problems/kth-smallest-element-in-a-bst/submissions/) | [题解](https://leetcode.cn/problems/kth-smallest-element-in-a-bst/solution/)
Solutions & Notes
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