1.struct ListNode* deleteDuplicates(struct ListNode* head) {
    if (!head) {
        return head;
    }

    struct ListNode* dummy = malloc(sizeof(struct ListNode));
    dummy->next = head;

    struct ListNode* cur = dummy;
    while (cur->next && cur->next->next) {
        if (cur->next->val == cur->next->next->val) {
            int x = cur->next->val;
            while (cur->next && cur->next->val == x) {
                cur->next = cur->next->next;
            }
        } else {
            cur = cur->next;
        }
    }

    return dummy->next;
}

作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/solution/shan-chu-pai-xu-lian-biao-zhong-de-zhong-oayn/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if (!head || !head->next) {
            return head;
        }
        if (head->val != head->next->val) {
            head->next = deleteDuplicates(head->next);
        } else {
            ListNode* move = head->next;
            while (move && head->val == move->val) {
                move = move->next;
            }
            return deleteDuplicates(move);
        }
        return head;
    }
};

作者：fuxuemingzhu
链接：https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/solution/fu-xue-ming-zhu-di-gui-die-dai-yi-pian-t-wy0h/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。