LeetCode101--对称二叉树

 1 '''
 2 给定一个二叉树，检查它是否是镜像对称的。
 3 '''
 4 
 5 
 6 class TreeNode:
 7     def __init__(self, x):
 8         self.val = x
 9         self.left = None
10         self.right = None
11 
12 
13 class Solution:
14     def isSymmetric(self, root):
15         """
16         :type root: TreeNode
17         :rtype: bool
18         """
19         if not root:
20             return True
21         else:
22             # p=root.left;q=root.right
23             def isSameTree(p, q):
24                 if not p and not q:  # 两二叉树皆为空，递归边界，两者皆为空返回真
25                     return True
26                 if p and q and p.val == q.val:
27                     l = isSameTree(p.left, q.right)
28                     r = isSameTree(p.right, q.left)
29                     return l and r  # 需要l与r皆为true时，才返回真。只用最后一次递归边界return值
30                 else:
31                     return False
32 
33             return isSameTree(root.left, root.right)
34 
35 
36 if __name__ == '__main__':
37     n = [1, 2, 2, 3, 4, 4, 3]
38     root = TreeNode(1)
39     l1 = root.left = TreeNode(2)
40     r1 = root.right = TreeNode(2)
41     l2ll = l1.left = TreeNode(3)
42     l2lr = l1.right = TreeNode(4)
43     l2rl = r1.left = TreeNode(4)
44     l2rr = r1.right = TreeNode(3)
45     ret = Solution().isSymmetric(root)
46     print(ret)