leetcode:Symmetric Tree【Python版】

#error caused by：
#1:{} 没有考虑None输入
#2:{1,2,2} 没有控制h和t
#3：{4,-57,-57,#,67,67,#,#,-97,-97} 没有考虑负号，将s从str变成list，采用9999代表空数值；

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逐层进行对称性验证，出现不对称就结束；

 # 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 isSymmetric(self,root):
         ret = True
         q = []
         s = []
         if root != None:#注意root为空
             q.append(root)
             s.append(root.val)
         while (len(q) != 0 and ret == True):
             h = 0
             t = len(s) - 1
             while (h < t):
                 if (s[h] != s[t]):
                     ret = False
                     break
                 h+=1#这里忘记控制h和t了
                 t-=1
             tq = q
             s = []
             q = []
             while (len(tq) != 0 and ret == True):
                 t = tq.pop(0)#pop默认弹出最后一个值
                 if t.left != None:
                     q.append(t.left)
                     s.append(t.left.val)
                 else:
                     s.append(9999)
                 if t.right != None:
                     q.append(t.right)
                     s.append(t.right.val)
                 else:
                     s.append(9999)
         return ret