前、中、后序遍历(递归版本)
def preOrder(self, root):
if root is None:
return []
else:
return [root.val] + self.preOrder(root.left) + self.preOrder(root.right)
def inOrder(self, root):
if root is None:
return []
else:
return self.inOrder(root.left) + [root.val] + self.inOrder(root.right)
def postOrder(self, root):
if root is None:
return []
else:
return self.postOrder(root.left) + self.postOrder(root.right) + [root.val]