Python iterative solution with the dummy root

  • 1
    def upsideDownBinaryTree(self, root):
            stack = []
            while root:
                root = root.left
            dummy = TreeNode(None)
            curr = dummy
            while stack:
                node = stack.pop()
                curr.right = node
                curr.left = node.right
                curr = curr.right
            curr.left = curr.right = None
            return dummy.right

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