LeetCode-101-Symmetric Tree judge对称tree

save all the nodes including None in a 2-dimension list and judge the symmetry

# 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):
    ans=[]
    def isSymmetric(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        if root==None:return True
        
        self.ans=[]
        self.dfs(root,1)
        Len=len(self.ans)
        for i in range(1,Len):
            curLen=len(self.ans[i])
            if curLen&1:return False
            for j in range(curLen/2):
                if self.ans[i][j]!=self.ans[i][curLen-j-1]:return False
        return True
    def dfs(self,root,deep):
        if root==None:
            if len(self.ans)<deep:
                self.ans.append([-1])
            else:
                self.ans[deep-1].append(-1)
            return
        
        if len(self.ans)<deep:
            self.ans.append([root.val])
        else:
            self.ans[deep-1].append(root.val)
        
        self.dfs(root.left,deep+1)
        self.dfs(root.right,deep+1)