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.res1 = []
        self.res2 = []
        self.res3 = []
        
    def threeOrders(self , root: TreeNode) -> List[List[int]]:
        # write code here
        self.preorder(root)
        self.inorder(root)
        self.postorder(root)
        return [self.res1,self.res2,self.res3]

    def preorder(self,root):
        if not root:
            return
        self.res1.append(root.val)
        self.preorder(root.left)
        self.preorder(root.right)
    
    def inorder(self,root):
        if not root:
            return 
        self.inorder(root.left)
        self.res2.append(root.val)
        self.inorder(root.right)
        
    def postorder(self,root):
        if not root:
            return 
        self.postorder(root.left)
        self.postorder(root.right)
        self.res3.append(root.val)