[leetcode]#101. Symmetric Tree

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

class Solution:
# @param root, a tree node
# @return a boolean
def help(self, p, q):
if p == None and q == None: return True
if p and q and p.val == q.val:
return self.help(p.right, q.left) and self.help(p.left, q.right)
return False

def isSymmetric(self, root):
if root:
return self.help(root.left, root.right)
return True