def delNodes(self, root, to_delete):
        '''
        Use bottom up appraoch: if my left/right is part of delete list, I will cut my left/right branch
        if I am part of delete list, I will add my left/right pointers #if exist# => return True
        otherwise: return False (meaning I'm not part of delete list, don't worry about me)

        P.S: if my left/right pointers were part of delete list they would have already been taken care of in my previous recurion call, that's why bottom-up approach is better and no need to track the parent pointer.
        '''
        if root is None:
            return []
        del_set=set(to_delete)

        def delete(root,del_set,root_list):
            if root is None:
                return False

            pleft=delete(root.left,del_set,root_list)
            pright=delete(root.right,del_set,root_list)

            if pleft:
                root.left=None
            if pright:
                root.right=None
            if root.val in del_set:
                if root.left:
                    root_list.append(root.left)
                if root.right:
                    root_list.append(root.right)
                return True
            return False

        root_list=[]
        if root.val not in del_set:
            root_list.append(root)
        delete(root,del_set,root_list)
        return root_list