Project Notes

Validate Binary Search Tree

3 min read

Nav: << previous: 97.交错字符串 | next: 99.恢复二叉搜索树 >>

Description

tab: English
 
<p>Given the <code>root</code> of a binary tree, <em>determine if it is a valid binary search tree (BST)</em>.</p>
 
<p>A <strong>valid BST</strong> is defined as follows:</p>
 
<ul>
	<li>The left <span data-keyword="subtree">subtree</span> of a node contains only nodes with keys&nbsp;<strong>strictly less than</strong> the node&#39;s key.</li>
	<li>The right subtree of a node contains only nodes with keys <strong>strictly greater than</strong> the node&#39;s key.</li>
	<li>Both the left and right subtrees must also be binary search trees.</li>
</ul>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/01/tree1.jpg" style="width: 302px; height: 182px;" />
<pre>
<strong>Input:</strong> root = [2,1,3]
<strong>Output:</strong> true
</pre>
 
<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/01/tree2.jpg" style="width: 422px; height: 292px;" />
<pre>
<strong>Input:</strong> root = [5,1,4,null,null,3,6]
<strong>Output:</strong> false
<strong>Explanation:</strong> The root node&#39;s value is 5 but its right child&#39;s value is 4.
</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 10<sup>4</sup>]</code>.</li>
	<li><code>-2<sup>31</sup> &lt;= Node.val &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/validate-binary-search-tree/submissions/) | [solutions](https://leetcode.com/problems/validate-binary-search-tree/solutions/)
 
 
tab: 中文
 
<p>给你一个二叉树的根节点 <code>root</code> ，判断其是否是一个有效的二叉搜索树。</p>
 
<p><strong>有效</strong> 二叉搜索树定义如下：</p>
 
<ul>
	<li>节点的左<span data-keyword="subtree">子树</span>只包含<strong>&nbsp;严格小于 </strong>当前节点的数。</li>
	<li>节点的右子树只包含 <strong>严格大于</strong> 当前节点的数。</li>
	<li>所有左子树和右子树自身必须也是二叉搜索树。</li>
</ul>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/01/tree1.jpg" style="width: 302px; height: 182px;" />
<pre>
<strong>输入：</strong>root = [2,1,3]
<strong>输出：</strong>true
</pre>
 
<p><strong>示例 2：</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/12/01/tree2.jpg" style="width: 422px; height: 292px;" />
<pre>
<strong>输入：</strong>root = [5,1,4,null,null,3,6]
<strong>输出：</strong>false
<strong>解释：</strong>根节点的值是 5 ，但是右子节点的值是 4 。
</pre>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li>树中节点数目范围在<code>[1, 10<sup>4</sup>]</code> 内</li>
	<li><code>-2<sup>31</sup> &lt;= Node.val &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/validate-binary-search-tree/submissions/) | [题解](https://leetcode.cn/problems/validate-binary-search-tree/solution/)

Solutions & Notes

properties:
  note.updated:
    displayName: Last Updated
  note.relative_links:
    displayName: Related Links
  note.desc:
    displayName: Description
  note.grade:
    displayName: Rating
  note.program_language:
    displayName: Language
  note.time_complexity:
    displayName: TC
  note.space_complexity:
    displayName: SC
views:
  - type: table
    name: Solutions & Notes
    filters:
      and:
        - file.hasLink(this.file)
        - file.tags.containsAny("leetcode/solution", "leetcode/note")
    order:
      - file.name
      - desc
      - program_language
      - time_complexity
      - space_complexity
      - grade
      - relative_links
      - updated
    sort:
      - property: grade
        direction: ASC
      - property: time_complexity
        direction: ASC
      - property: program_language
        direction: ASC
    columnSize:
      file.name: 104
      note.space_complexity: 65
      note.grade: 126

Similar Problems

properties:
  note.lcTopics:
    displayName: Topics
  note.lcAcRate:
    displayName: AC Rate
  note.favorites:
    displayName: Favorites
  note.grade:
    displayName: Rating
  note.translatedTitle:
    displayName: Title (CN)
  note.lcDifficulty:
    displayName: Difficulty
views:
  - type: table
    name: Similar Problems
    filters:
      and:
        - file.hasLink(this.file)
        - similarQuestions.contains(this.file)
    order:
      - file.name
      - translatedTitle
      - lcTopics
      - lcDifficulty
      - lcAcRate
      - grade
      - favorites
    sort:
      - property: file.name
        direction: ASC
      - property: lcTopics
        direction: DESC
    columnSize:
      note.translatedTitle: 240
      note.lcTopics: 347
      note.lcAcRate: 75
      note.grade: 122

Graph View

Backlinks