Insertion Sort List

public static ListNode insertionSortList( ListNode head ) {
    ListNode dummyHead = new ListNode( 0 );
    while( head != null ) {
        ListNode next = head.next;
        ListNode pre = dummyHead;
        while( pre.next != null && pre.next.val < head.val )
            pre = pre.next;
        head.next = pre.next;
        pre.next = head;
        head = next;
    }
    return dummyHead.next;
}