对称二叉树

Python

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
	def isSymmetric(self, root):
		"""
		:type root: TreeNode
		:rtype: bool
		"""
		if not root:
			return True
		def dfs(left,right):
			if not (left or right):
				return True
			if not (left and right):
				return False
			if left.val!=right.val:
				return False
			return dfs(left.left,right.right) and dfs(left.right,right.left)
		return dfs(root.left,root.right)