[easy+][Tree] 101.Symmetric Tree

原题是：

Screen Shot 2017-11-07 at 1.54.16 PM.png

思路是：

将给定的整颗树，进行复制。对复制的树，进行左右翻转操作，再对比翻转好的树，和原先的树是否是一样的树。
这里要注意的是，我犯过一个错误，将原先的树翻转之后，丢失原先的树了。所以增加了一个迭代函数对原先的树进行拷贝。

代码是：

# 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):
    # deep copy tree root
   
        
    def reverse(self,root):
        if root == None:
            return root
        else:
            tmp = root.left
            root.left = root.right
            root.right = tmp
            root.left = self.reverse(root.left)
            root.right = self.reverse(root.right)
            return root
    
    def isSame(self,root1,root2):
        
        if root1 == None and root2 == None:
            return True
        elif not (root1 and root2):
            return False
        #elif not (root1.left or root1.right or root2.left or root2.right) and root1.val == root2.val:
        #    return True
        elif root1.val != root2.val:
            return False
        
        return self.isSame(root1.left,root2.left) and self.isSame(root1.right,root2.right)        
    

    def isSymmetric(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        root = copy.deepcopy(root)
        root_reverse = self.reverse(root_reverse)
        
        return self.isSame(root,root_reverse)