Question：

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.

Algorithm：

见程序

Accepted Code：

/**
 * 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;            //前
        while(p!=NULL&&p->next!=NULL)
        {
           ListNode *q=p->next;
           if(q->val==p->val)
           {
               p->next=q->next;
               delete q;
           }
           else
           {
               p=p->next;
           }
        }
        return head;
    }
};