82. 删除排序链表中的重复元素 II

原题链接：82. 删除排序链表中的重复元素 II

solution:

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if(head == nullptr || head->next == nullptr) return head;
        ListNode *dummy = new ListNode(-1);
        ListNode *pre = dummy;
        ListNode *cur = head;
        dummy->next = head;
        while(cur != nullptr && cur->next != nullptr) {
            if(cur->val == cur->next->val) {
                while(cur->next != nullptr && cur->val == cur->next->val) { //跳过所有重复节点
                    cur = cur->next;
                }
                pre->next = cur->next;
                cur = cur->next;
            }else { //不是重复节点正常遍历
                pre = pre->next;    
                cur = cur->next;
            }
        }
        return dummy->next;
    }
};