101 Symmetric Tree

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool isSymmetric(TreeNode* root) {
if(root==NULL)
return true;
return isSymmetric(root->left, root->right);
}
bool isSymmetric(TreeNode* p, TreeNode* q) {
if(p==NULL&&q==NULL)
return true;
if(p==NULL||q==NULL)
return false;
if(p->val!=q->val)
return false;
return isSymmetric(p->left, q->right)&&isSymmetric(q->left, p->right);

}
};