Example #1
0
    def flatten(self, root: TreeNode) -> None:
        if root is None:
            return

        numList = []
        self.preOrder(root, numList)
        root.val = numList[0]
        root.left = None
        cur = root
        for i in range(1, len(numList)):
            cur.right = TreeNode(numList[i])
            cur = cur.right