Remove Duplicates from Sorted List 去除链表重复数据

Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear only once.
For example,

Given

1->1->2

, return

1->2

.

Given

1->1->2->3->3

, return

1->2->3

.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        if(head==NULL||head->next==NULL)
            return head;
        ListNode *p=head,*help=new ListNode(-9999999);
        while(p!=NULL)
        {
            ListNode *next=p->next;
            if(p->val!=help->val)
            {
                help->next=p;
                help=p;
                help->next=NULL;
            }
            else{
                delete p;
            }
            p=next;
        }
        
        return head;
    }
};