public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
      ListNode value=new ListNode(Integer.MIN_VALUE);
      ListNode team=value;
      while (l1!=null||l2!=null) {
		if(l1==null)
		{
			team.next=l2;break;
		}
		else if (l2==null) {
			team.next=l1;break;
		}
		else {
			if(l1.val<l2.val)
			{
				team.next=new ListNode(l1.val);
				team=team.next;
				l1=l1.next;
			}
			else {
				team.next=new ListNode(l2.val);
				team=team.next;
				l2=l2.next;
			}
		  }
	   }
       return value.next;
  }

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
	  if(l1==null)return l2;
	  if(l2==null)return l1;
	  if(l1.val>l2.val)//l1更小
	  {
		  ListNode team=l1;
		  l1=l2;
		  l2=team;
	  }
      ListNode value=l1;
      while (l2!=null) {
		if(l1.next==null)
		{
			l1.next=l2;break;
		}
		else if (l1.next.val<l2.val) {
			l1=l1.next;
		}
		else {
			ListNode node=l1.next;
			l1=l1.next=l2;
			l2=node;
			//l1=l1.next;
			
		}
	   }
       return value; 
  }