连接两个单向链表，返回排序后的结果。

     本题目解答思路：（1）先将两个无序的链接排序（2）将排序后的列表合并  
     // 链表类  
      class ListNode {  
      int val;  
      ListNode next = null;  
      
  
      ListNode(int val) {  
      this.val = val;  
      }  
      }  
      
  

  // 连接两个单项链表，返回排序后的结果 
  public static ListNode unionTwoLinkTable(ListNode list1,  ListNode list2) { 
  if (list1 != null) { 
  // 将list1变为有序的 
  for (ListNode ln1 = list1; ln1.next != null; ln1 =  ln1.next) { 
  if (ln1.val > ln1.next.val) { 
  int temp = ln1.val; 
  ln1.val = ln1.next.val; 
  ln1.next.val = temp; 
  } 
  } 
  } 
  if (list2 != null) { 
  // 将list2变为有序的 
  for (ListNode ln2 = list2; ln2.next != null; ln2 =  ln2.next) { 
  if (ln2.val > ln2.next.val) { 
  int temp = ln2.val; 
  ln2.val = ln2.next.val; 
  ln2.next.val = temp; 
  } 
  } 
  } 
  

  ListNode head, tmp; 
  if (list1.val <= list2.val) { 
  tmp = list1; 
  list1 = list1.next; 
  } else { 
  tmp = list2; 
  list2 = list2.next; 
  } 
  head = tmp; 
  while (list1 != null && list2 != null) { 
  if (list1.val <= list2.val) { 
  tmp.next = list1; 
  tmp = list1; 
  list1 = list1.next; 
  } else { 
  tmp.next = list2; 
  tmp = list2; 
  list2 = list2.next; 
  } 
  } 
  if (list1 != null) 
  tmp.next = list1; 
  if (list2 != null) 
  tmp.next = list2; 
  return head; 
  } 
  //输出 
     public static ArrayList<Integer>    printListFromTailToHead(ListNode listNode) {  
      ArrayList<Integer> li = new    ArrayList<Integer>();  
      if (listNode == null) {  
      return li;  
      }  
      li.add(listNode.val);  
      for (ListNode ln = listNode.next; ln != null; ln =    ln.next) {  
      li.add(ln.val);  
      }  
      for (int i = 0; i < li.size(); i++)  
      System.out.print(li.get(i) + "  ");  
      System.out.println();  
      return li;  
      }