#82删除排序链表中的重复元素 II

public class Solution {
    static final class ListNode {
        int val;
        ListNode next;
        ListNode(int val) { this.val = val; }
        ListNode(int val, ListNode next) { this.val = val; this.next = next; }
    }

    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(0, head);
        ListNode prev = dummy;
        while (prev.next != null && prev.next.next != null) {
            if (prev.next.val != prev.next.next.val) {
                prev = prev.next;
                continue;
            }
            int duplicate = prev.next.val;
            while (prev.next != null && prev.next.val == duplicate) {
                prev.next = prev.next.next;
            }
        }
        return dummy.next;
    }
}