LeetCode83: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.

对于这个删除链表中的重复元素但是对于重复元素需要保留一个，前面遇到的的重复元素是出现在前面还是中间这个问题就没有了，依次执行删除即可。
runtime:16ms

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

        }
        return tmp;
    }
};