125. Invert/Flip Binary Tree

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Input: root = [4,2,7,1,3,6,9]

Output: [4,7,2,9,6,3,1]

Explanation: The tree is inverted such that the left and right subtrees of each node are swapped.

Input: root = [2,1,3]

Output: [2,3,1]

Explanation: The tree with root 2 has its left child 1 and right child 3 swapped.

Input: root = []

Output: []

Explanation: An empty tree remains an empty tree after inversion.

Time Complexity

O(n)

Space Complexity

O(h)