82. Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

含义：如果列表中有重复数字的，把他们全部删除掉

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