26 lines
948 B
Markdown
26 lines
948 B
Markdown
You are given the `root` of a binary search tree (BST), where the values of **exactly** two nodes of the tree were swapped by mistake. _Recover the tree without changing its structure_.
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**Example 1:**
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Input: root = [1,3,null,null,2]
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Output: [3,1,null,null,2]
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Explanation: 3 cannot be a left child of 1 because 3 > 1. Swapping 1 and 3 makes the BST valid.
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**Example 2:**
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Input: root = [3,1,4,null,null,2]
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Output: [2,1,4,null,null,3]
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Explanation: 2 cannot be in the right subtree of 3 because 2 < 3. Swapping 2 and 3 makes the BST valid.
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**Constraints:**
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* The number of nodes in the tree is in the range `[2, 1000]`.
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* `-231 <= Node.val <= 231 - 1`
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**Follow up:** A solution using `O(n)` space is pretty straight-forward. Could you devise a constant `O(1)` space solution? |