Same Tree [LeetCode]

class Solution {
public:
bool isSameTree(TreeNode *p, TreeNode *q) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(p == NULL && q == NULL)
return true;
if(p == NULL && q != NULL ||
(p != NULL && q == NULL))
return false;
if(p->val != q->val)
return false;
return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
}
};