Leetcode 83. 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.

s思路：
1. 和82题相似。用pre和pnow,但不用dummy或pointer to pointer,因为头节点不变。

class Solution {public:    ListNode* deleteDuplicates(ListNode* head) {        //        ListNode* pre=head,*pnow=head;        while(pnow){//第一个while遍历整个链表            while(pnow->next&&pnow->next->val==pnow->val)//第二个while遍历重复的元素                pnow=pnow->next;            if(pnow!=pre){                pre->next=pnow->next;                   }                            pre=pre->next;            pnow=pnow->next;        }        return head;    }};