class : def__init__(self, x): self.val = x self.left = None self.right = None
classSolution: defhelper(self, root, res): if root: res.append(1) if root.left: self.helper(root.left, res) if root.right: self.helper(root.right, res)
defcountNodes(self, root): """ :type root: TreeNode :rtype: int """ res = [] self.helper(root, res) return len(res)
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