【Leetcode】Remove Duplicates from Sorted List II

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode *deleteDuplicates(ListNode *head) {
12         if (head == nullptr || head->next == nullptr) 
13             return head;
14         ListNode dummy(-1);
15         dummy.next = head;
16         ListNode *prev = &dummy, *cur = head;
17         while (cur != nullptr) {
18             bool flag = false;
19             while (cur->next != nullptr && cur->val == cur->next->val) {
20                 flag = true;
21                 prev->next = cur->next;
22                 delete cur;
23                 cur = prev->next;
24             }
25             if (flag) {
26                 prev->next = cur->next;
27                 delete cur;
28                 cur = prev->next;
29             } else {
30                 prev = cur;
31                 cur = cur->next;
32             }
33         }
34         return dummy.next;
35     }
36 };