https://leetcode-cn.com/problems/same-tree/
    需要注意的点

    1. # Definition for a binary tree node.
    2. # class TreeNode:
    3. #     def __init__(self, val=0, left=None, right=None):
    4. #         self.val = val
    5. #         self.left = left
    6. #         self.right = right
    7. class Solution:
    8.     def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
    9.         if not p and not q:
    10.             return True
    12.         if (not p or not q) or p.val != q.val:
    13.             return False
    17.         def reverseTree(n1: TreeNode, n2: TreeNode)->bool:
    18.             if not n1 or not n2:   
    19.                 return n1 == n2
    21.             if n1.val != n2.val:
    22.                 return False
    24.             return reverseTree(n1.left, n2.left) and reverseTree(n1.right, n2.right)
    27.         return reverseTree(p, q)