Symmetric Tree (Iteratively)

/**
	 * 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.
	 * 
	 * */