How should I practice Recover Binary Search Tree?

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Recover Binary Search Tree

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Problem statement

You are given the root of a binary search tree in which the values of exactly two nodes were swapped by mistake. Restore the binary search tree without changing its structure.

The callable returns the same root after recovery so the judge can serialize and compare the corrected tree.

Function

recoverTree(root: TreeNode) → TreeNode

Examples

Example 1

root = [1,3,null,null,2]return = [3,1,null,null,2]

The value 3 cannot be the left child of 1 in a valid binary search tree. Swapping 1 and 3 restores the ordering.

Example 2

root = [3,1,4,null,null,2]return = [2,1,4,null,null,3]

The inorder sequence is [1,3,2,4]. Swapping the misplaced values 3 and 2 makes it increasing.

Example 3

root = [2,3,1]return = [2,1,3]

The two child values are reversed. Swapping them preserves the three-node structure and restores the tree.

Constraints

The tree contains between 2 and 1000 nodes.
-2^31 <= Node.val <= 2^31 - 1
The input was a valid binary search tree before exactly two node values were exchanged.