83. Remove Duplicates from Sorted List

 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 static int wing=[]()
10 {
11     std::ios::sync_with_stdio(false);
12     cin.tie(NULL);
13     return 0;
14 }();
15 
16 
17 class Solution 
18 {
19 public:
20     ListNode* deleteDuplicates(ListNode* head) 
21     {
22         if(head==NULL||head->next==NULL)
23             return head;
24         ListNode *pre=head,*beh=head->next;
25         while(beh)
26         {
27             if(pre->val==beh->val)
28             {
29                 beh=beh->next;
30                 pre->next=beh;
31             }
32             else
33             {
34                 pre=beh;
35                 beh=beh->next;
36             }
37         }
38         return head;
39     }
40 };

俩指针，前后节点值比较，相等的话，后指针后移，前指针的后继随之后移

不相等的话，俩指针同时后移，直到后指针为空表示链表扫描完毕