第二题： void removeDuplicates(ListNode *head) {     // 在这里编写代码     ListNode *p = head;     while(p != NULL && p->next != NULL){         ListNode *p1 = p->next;         if(p->val != p1->val){             p1 = p1->next;             p = p->next;             continue;         }         while(p1->next != NULL && p1->next->val == p->val)             p1 = p1->next;         p->next = p1;         p = p->next;         p1 = p1->next;     } }