Leetcode【101】Symmetric Tree （Python版）

python函数中定义函数，只能这么写

# 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
        """

        def helper(t1,t2):
            if not t1 and not t2:
                return True
            if not t1 or not t2:
                return False
            return (t1.val == t2.val) and helper(t1.left,t2.right) and helper(t1.right,t2.left)

        return helper(root,root)