Remove Duplicates from Sorted List II -interesting

 //from anniekim, iterative
    ListNode *deleteDuplicates(ListNode *head) {
        ListNode dummy(0);dummy.next=head;
        ListNode *prev=&dummy;
        while(prev->next){
            int val=prev->next->val;
            ListNode *node=prev->next;
            if(!node->next||node->next->val!=val){
                prev=prev->next;
                continue;
            }
            while(node&&node->val==val){
                ListNode*del=node;
                node=node->next;
                delete del;
            }
            prev->next=node;
        }
        return dummy.next;

    }

//recursive
ListNode *deleteDuplicates(ListNode *head) {
    if (!head) return NULL;
    if (!head->next || head->val != head->next->val) {
        head->next = deleteDuplicates(head->next);
        return head;
    }
    int val = head->val;
    while(head && head->val == val) {
        ListNode *del = head;
        head = head->next;
        delete del;
    }
    return deleteDuplicates(head);
}