# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def inOrder(self,root,nums):
        if not root:
            return 
        if not root.left and not root.right:
            nums.append(root.val)
            return 
        if root.left:
            self.inOrder(root.left,nums)
        else:
            nums.append(None)

        nums.append(root.val)

        if root.right:
            self.inOrder(root.right,nums)
        else:
            nums.append(None)
        
        
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        nums_left = []
        nums_right = []
        # 如果对称，左右子树中序遍历结果对调
        self.inOrder(root.left,nums_left)
        self.inOrder(root.right,nums_right)
        if len(nums_left)!=len(nums_right):
            return False
        low = 0
        high = len(nums_left)-1
        print(nums_left)
        print(nums_right)
        while low<=high:
            if nums_left[low]!=nums_right[high]:
                return False
            low+=1
            high-=1
        return True