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36 lines
1.2 KiB
HTML
36 lines
1.2 KiB
HTML
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<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>
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<p><strong>有效</strong> 二叉搜索树定义如下：</p>
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<ul>
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<li>节点的左子树只包含<strong> 小于 </strong>当前节点的数。</li>
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<li>节点的右子树只包含 <strong>大于</strong> 当前节点的数。</li>
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<li>所有左子树和右子树自身必须也是二叉搜索树。</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/2020/12/01/tree1.jpg" style="width: 302px; height: 182px;" />
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<pre>
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<strong>输入：</strong>root = [2,1,3]
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<strong>输出：</strong>true
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</pre>
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<p><strong>示例 2：</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/12/01/tree2.jpg" style="width: 422px; height: 292px;" />
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<pre>
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<strong>输入：</strong>root = [5,1,4,null,null,3,6]
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<strong>输出：</strong>false
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<strong>解释：</strong>根节点的值是 5 ，但是右子节点的值是 4 。
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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>树中节点数目范围在<code>[1, 10<sup>4</sup>]</code> 内</li>
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<li><code>-2<sup>31</sup> <= Node.val <= 2<sup>31</sup> - 1</code></li>
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</ul>
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