面试题：删除链表中的重复节点

//如果全是1输出为空 执行过程
public class Solution {
    public ListNode deleteDuplication(ListNode pHead){
        ListNode first=new ListNode(0);
        first.next=pHead;
        ListNode last=first;
        while(pHead!=null&&pHead.next!=null){
            if(pHead.val==pHead.next.val){
                int val=pHead.val;
                //不加pHead!=null会报出空指针异常
                while(pHead!=null&&pHead.val==val){
                    pHead=pHead.next;
                }
                //last.next = p;的目的是跳出重复节点
                last.next=pHead;
            }else{
                //last=pHead;
                last.next=pHead;
                last=last.next;
                pHead=pHead.next;
            }
        }
        return first.next;
    }
}