// By CHOUBIK Houssam - Time complexity O(n)

bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
    if(p==NULL && q==NULL){
        return true;
    }
    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);

}