partition list

public ListNode partition(ListNode head, int x) {
        ListNode little = new ListNode(-2);
        ListNode large = new ListNode(-1);
        ListNode p1 = little;
        ListNode p2 = large;
        while (head != null) {
            if (head.val < x) {
                p1.next = head;
                p1 = p1.next;
            } else {
                p2.next = head;
                p2 = p2.next;
            }
            head = head.next;
        }
        p2.next = null;
        p1.next = large.next;
        return little.next;
    }