class Solution {public:    bool isSameTree(TreeNode* p, TreeNode* q) {        if(p == NULL && q == NULL)            return true;        else if(p == NULL || q == NULL)            return false;        if(p->val != q->val)            return false;        return isSameTree(p->left,q->left) && isSameTree(p->right,q->right);    }};