leetcode100 Same Tree

 1 """
 2 Given two binary trees, write a function to check if they are the same or not.
 3 Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
 4 Example 1:
 5 Input:     1         1
 6           /        / 
 7          2   3     2   3
 8         [1,2,3],   [1,2,3]
 9 Output: true
10 Example 2:
11 Input:     1         1
12           /           
13          2             2
14         [1,2],     [1,null,2]
15 Output: false
16 Example 3:
17 Input:     1         1
18           /        / 
19          2   1     1   2
20         [1,2,1],   [1,1,2]
21 Output: false
22 """
23 class TreeNode:
24     def __init__(self, x):
25         self.val = x
26         self.left = None
27         self.right = None
28 
29 class Solution:
30     def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
31         if p ==  None and q == None:
32             return True
33         # bug代码
34         # flag = False
35         # while p and q:
36         #     if p.val == q.val:
37         #         self.isSameTree(p.left, q.left)
38         #         self.isSameTree(q.right, q.right)
39         #         flag = True
40         # return flag
41         # 递归注意不用while循环，也应当注意return返回值
42         if p and q and p.val == q.val:
43             return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)