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29 lines
1.4 KiB
HTML
29 lines
1.4 KiB
HTML
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<p>You are given the <code>root</code> of a binary search tree (BST), where the values of <strong>exactly</strong> two nodes of the tree were swapped by mistake. <em>Recover the tree without changing its structure</em>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/10/28/recover1.jpg" style="width: 422px; height: 302px;" />
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<pre>
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<strong>Input:</strong> root = [1,3,null,null,2]
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<strong>Output:</strong> [3,1,null,null,2]
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<strong>Explanation:</strong> 3 cannot be a left child of 1 because 3 > 1. Swapping 1 and 3 makes the BST valid.
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</pre>
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<p><strong>Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/10/28/recover2.jpg" style="width: 581px; height: 302px;" />
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<pre>
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<strong>Input:</strong> root = [3,1,4,null,null,2]
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<strong>Output:</strong> [2,1,4,null,null,3]
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<strong>Explanation:</strong> 2 cannot be in the right subtree of 3 because 2 < 3. Swapping 2 and 3 makes the BST valid.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li>The number of nodes in the tree is in the range <code>[2, 1000]</code>.</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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<p> </p>
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<strong>Follow up:</strong> A solution using <code>O(n)</code> space is pretty straight-forward. Could you devise a constant <code>O(1)</code> space solution?
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