public ListNode Merge(ListNode list1,ListNode list2) {//链表 my

         ListNode head = new ListNode(0);

         ListNode cur = head;

         while(list1!=null&&list2!=null){

             if(list1.val<list2.val){

                 cur.next = list1;

                 list1 = list1.next;

             }

             else{

                 cur.next = list2;

                 list2=list2.next;

             }

             cur = cur.next;

         }

         if(null == list1){

             cur.next =  list2;

         }

         if(null == list2){

             cur.next =  list1;

         }

         return head.next;

     }

public ListNode Merge(ListNode list1,ListNode list2) {//链表 递归my

        if(null == list1){

            return list2;

        }

        if(null == list2){

            return list1;

        }

        ListNode result = null;

        if(list1.val <= list2.val){

            result = list1;

            result.next= Merge(list1.next,list2);

        }

        else{

            result = list2;

            result.next=Merge(list1,list2.next);

        }

        return result;

    }