从链接列表中删除和添加项目（Java）

Question

当我尝试测试用例时，我编写的代码不起作用，但我不明白为什么。 我的代码在2种方法中。 如果您需要其余的类文件，可以在https://www.cs.berkeley.edu/~jrs/61b/hw/hw3/中找到它们。 注意我编辑了节点类并创建了set和get方法。 难道是给我错误还是我的解决方案是错误的？

/**
*  squish() takes this list and, wherever two or more consecutive items are
*  equals(), it removes duplicate nodes so that only one consecutive copy
*  remains.  Hence, no two consecutive items in this list are equals() upon
*  completion of the procedure.
*
*  After squish() executes, the list may well be shorter than when squish()
*  began.  No extra items are added to make up for those removed.
*
*  For example, if the input list is [ 0 0 0 0 1 1 0 0 0 3 3 3 1 1 0 ], the
*  output list is [ 0 1 0 3 1 0 ].
*
*  IMPORTANT:  Be sure you use the equals() method, and not the "=="
*  operator, to compare items.
**/

public void squish() {
// Fill in your solution here.  (Ours is eleven lines long.)
  SListNode previous = head;
  SListNode next;
  SListNode root = head;
  int x = 1;

  for (int counter = 0; counter < size; counter++)
  {
      next = previous.getNext();
      if (!previous.equals(next))
      {
          root.setNext(next);
          root = next;
          x++;
      }
      previous = previous.getNext();

  }
  size = x;
}

/**
*  twin() takes this list and doubles its length by replacing each node
*  with two consecutive nodes referencing the same item.
*
*  For example, if the input list is [ 3 7 4 2 2 ], the
*  output list is [ 3 3 7 7 4 4 2 2 2 2 ].
*
*  IMPORTANT:  Do not try to make new copies of the items themselves.
*  Make new SListNodes, but just copy the references to the items.
**/

public void twin() {
 // Fill in your solution here.  (Ours is seven lines long.)
 SListNode previous = head;
 SListNode next;

 for (int counter = 0; counter < size; counter++)
 {
     next = previous.getNext();
     previous.setNext(previous);
     previous = previous.getNext();
     previous.setNext(next);
 }
 size = 2*size;
}

Answer 1

我认为这可能是列表长度在完成时未更新的问题。 当您忘记这样做时，测试用例可能会寻找并打印出错误消息！ （没有饼干！）

虽然我不确定，但这似乎是最合理的解释（查看测试文件，看看他们如何明确声明检查所有不变量）。