树的便利

前序(Pre-order)

• 根-左-右

def preorder(self,root):
    if root:
        self.traverse_path.append(root.val)
        self.preorder(root.left)
        self.preorder(root.right)

中序(In-order)

• 左-根-右

def inorder(self,root):
    if root:
        self.inorder(root.left)
        self.traverse_path.append(root.val)
        self.inorder(root.right)

后序(Post-order)

• 左-右-根

def postorder(self,root):
    if root:
        self.postorder(root.left)
        self.postorder(root.right)
        self.traverse_path.append(root.val)