從鏈接列表中刪除和添加項目（Java）

Question

當我嘗試測試用例時，我編寫的代碼不起作用，但我不明白為什么。 我的代碼在2種方法中。 如果您需要其余的類文件，可以在https://www.cs.berkeley.edu/~jrs/61b/hw/hw3/中找到它們。 注意我編輯了節點類並創建了set和get方法。 難道是給我錯誤還是我的解決方案是錯誤的？

/**
*  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

我認為這可能是列表長度在完成時未更新的問題。 當您忘記這樣做時，測試用例可能會尋找並打印出錯誤消息！ （沒有餅干！）

雖然我不確定，但這似乎是最合理的解釋（查看測試文件，看看他們如何明確聲明檢查所有不變量）。