LeetCode101--对称二叉树

 '''
 给定一个二叉树，检查它是否是镜像对称的。
 '''

 class TreeNode:
     def __init__(self, x):
         self.val = x
         self.left = None
         self.right = None

 class Solution:
     def isSymmetric(self, root):
         """
         :type root: TreeNode
         :rtype: bool
         """
         if not root:
             return True
         else:
             # p=root.left;q=root.right
             def isSameTree(p, q):
                 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
                     return True
                 if p and q and p.val == q.val:
                     l = isSameTree(p.left, q.right)
                     r = isSameTree(p.right, q.left)
                     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
                 else:
                     return False

             return isSameTree(root.left, root.right)

 if __name__ == '__main__':
     n = [1, 2, 2, 3, 4, 4, 3]
     root = TreeNode(1)
     l1 = root.left = TreeNode(2)
     r1 = root.right = TreeNode(2)
     l2ll = l1.left = TreeNode(3)
     l2lr = l1.right = TreeNode(4)
     l2rl = r1.left = TreeNode(4)
     l2rr = r1.right = TreeNode(3)
     ret = Solution().isSymmetric(root)
     print(ret)