LintCode删除排序链表中的重复数字 II

public static ListNode deleteDuplicates(ListNode head) {    if(head == null || head.next == null) {        return head;    } else {        ListNode newHead = new ListNode(0);        newHead.next = head;        ListNode pre = newHead;        ListNode p = head;        ListNode next = null;        while(p != null && p.next != null) {            next = p.next;            if(p.val == next.val) {            while(next != null && p.val == next.val) {                next = next.next;            }            pre.next = next;            p = next;            } else {                pre = p;                p = p.next;            }        }        return newHead.next;    }}