Remove Duplicates from Sorted List

题目：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.

代码如下：

/** * 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 *pre=head,*cur=head->next;bool flag=false; //标志是否有重复元素while(cur!=NULL){while(cur!=NULL && pre->val==cur->val){cur=cur->next;flag=true;}//遍历链表结束或者出现不同元素 if(flag)  pre->next=cur;pre=pre->next;if(cur!=NULL) //处理链表最后几个元素相等的情况cur=cur->next;}return head;    }};