19. Recover BST

PRO

Hard

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Input: root = [1,3,null,null,2]

Output: [3,1,null,null,2]

Explanation: The nodes with values 1 and 3 are swapped to correct the BST.

Input: root = [3,1,4,null,null,2]

Output: [2,1,4,null,null,3]

Explanation: The nodes with values 3 and 2 are swapped to correct the BST.

Time Complexity

O(n)

Space Complexity

O(h)