题解 | #实现二叉树先序，中序和后序遍历#

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 the root of binary tree
# @return int整型二维数组
#
class Solution:
    def __init__(self):
        self.ls_pre=[]
        self.ls_in=[]
        self.ls_post=[]

    def pre_order(self,node):
        if node:
            self.ls_pre.append(node.val)
            self.pre_order(node.left)
            self.pre_order(node.right)
    
    def in_order(self,node):
        if node:
            self.in_order(node.left)
            self.ls_in.append(node.val)
            self.in_order(node.right)
    
    def post_order(self,node):
        if node:    
            self.post_order(node.left)
            self.post_order(node.right)
            self.ls_post.append(node.val)



    def threeOrders(self , root: TreeNode) -> List[List[int]]:
        res=[]
        self.pre_order(root)
        res.append(self.ls_pre)

        self.in_order(root)
        res.append(self.ls_in)

        self.post_order(root)
        res.append(self.ls_post)

        return res