public static ListNode deleteDuplicates(ListNode head) {
		if (null == head || null == head.next) return head;
		ListNode p = head.next;
		ListNode q = head;
		while (null != p) {
			if (p.val == q.val) {
				q.next = p.next;
			} else {
				q = q.next;
			}
			p = p.next;
		}
		return head;
	}