如果cur的下两个节点都存在, 并且两个节点的值都相同, 则开始删除和cur.next值相同的节点, 否则cur向前一步 @param head @return

class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) { this.val = val; }
    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}
// @lc code=start
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    /**
     * 如果cur的下两个节点都存在, 并且两个节点的值都相同,
     * 则开始删除和cur.next值相同的节点, 否则cur向前一步
     * @param head
     * @return
     */
    public ListNode deleteDuplicates(ListNode head) {
        ListNode dummy = new ListNode(-1000, head);
        ListNode cur = dummy;
        while (cur.next != null && cur.next.next != null) {
            int val = cur.next.val;
            if (cur.next.next.val == val) {
                while (cur.next != null && cur.next.val == val) {
                    cur.next = cur.next.next;
                }
            } else {
                cur = cur.next;
            }
        }
        return dummy.next;
    }
}