删除链表中重复的结点

public ListNode deleteDuplication(ListNode pHead)
    {
        if (pHead==null){
            return pHead;
        }
        ListNode pre=pHead;
        ListNode curr=pHead.next;
        while (curr!=null){
            if (curr.val==pre.val){//如果当前结点的值和前一结点重复
                pre.next=curr.next;
                curr=pre.next;
            }else {
                pre=curr;
                curr=curr.next;
            }
        }
        return pHead;
    }

 public ListNode deleteDuplication2(ListNode pHead) //重复元素一个都不保留
    {
        if (pHead == null) {
            return pHead;
        }
        ListNode headpre=new ListNode(0);//设headpre
        headpre.next=pHead;
        //{0,1,2,3,3,4,4,5}
        ListNode preNotParall = headpre;//记录上一个不重复的结点
        ListNode pre = pHead;
        ListNode curr = pHead.next;
        while (curr != null) {
            if (curr.val == pre.val) {//如果当前结点的值和前一结点重复
                //继续往下找,直到当前结点和前一结点值不同
                while (curr!=null&&curr.val == pre.val){
                    curr=curr.next;
                }
               preNotParall.next=curr;
               if (curr!=null){
                   pre=curr;
                   curr=pre.next;
               }else {
                   return headpre.next;
               }
            } else {
                preNotParall.next=pre;
                preNotParall=pre;
                pre = curr;
                curr = curr.next;
            }
        }
        return headpre.next;
    }