Q53: Invert / Flip Binary Tree. - DSA Patterns (Multi-Lang)

In Simple Words: Recursively swap root.left and root.right at every node from leaves to root (or preorder).

Time: $O(N)$ | Space: $O(H)$

Multi-Language SolutionsPython 3 • JavaScript • TypeScript • Java • C++

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class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def invertTree(root: TreeNode | None) -> TreeNode | None:
    if not root: return None
    root.left, root.right = invertTree(root.right), invertTree(root.left)
    return root