Sort List (medium)

 public ListNode sortList(ListNode head) {
        if(head==null){
            return head;
        }
        ListNode current = head;
        ListNode next = head.next;
        while(next != null){
            if(next.val <= current.val){
                int temp = next.val;
                next.val = current.val;
                current.val = temp;
            }
            if(next.next== null){
                current = current.next;
                next = current.next;
            }else{
                next = next.next;
            }


        }

        return head;
    }