Leetcode 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.

bool isSameTree(TreeNode *p, TreeNode *q) {
    if(p == NULL || q == NULL) return p == q;
    else return (p->val == q->val) && isSameTree(p->left, q->right) && isSameTree(p->right,q->left);
}

bool isSymmetric(TreeNode *root) {
    if(root == NULL) return true;
    if(root->left == NULL || root->right == NULL) return root->left == root->right;return isSameTree(root->left,root->right);
}