Create Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
For example, this binary tree is symmetric:
    1
   / \
  2   2
 / \ / \
3  4 4  3


But the following is not:

    1
   / \
  2   2
   \   \
   3    3


Note:
Bonus points if you could solve it both recursively and iteratively.
confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.