如何在自定义 OrderedLinkedList class 中显示从列表中删除了哪些元素？

Question

我正在使用嵌套的 Ordered ListNode class 实现自定义 Ordered LinkedList class。一切正常，但我试图通过访问已删除的元素来扩展它。

这不是必需的，但我很好奇这将如何工作，因为我只能使用我被指示创建的方法，它们是 boolean add()、boolean remove() 和 clear().

我也在跟踪每次修改，每次成功添加、删除或调用 clear() 都会增加。我可以简单地创建另一个 OrderedLinkedList，并将删除的元素添加到其中，但我觉得我添加了不必要的修改计数。

同样，这部分只是为了好玩，不是必需的。我觉得这会让我更深入地了解创建自定义 classes.

我将展示 remove 和 main 方法。无法更改删除方法签名。

public boolean remove(Comparable obj) {

    for(OrderedListNode element = head.next; element != tail; element = element.next) {

    if(obj.equals(element.dataItem)) { //if element being removed is at the cursor
        OrderedListNode previousNode = element.before;
        OrderedListNode nextNode = element.next;

        nextNode.before = previousNode; //places next element that's after before to the element after current element [prev -> current -> next]

        previousNode.next = nextNode; //places prev of next element to the element before current

        element.dataItem = (Comparable)NOT_FOUND; //removed element is now null

        modCount++; //another modification
        theSize--; //reduce the size by 1
        return true; //if remove is successful
    }
}
return false; //otherwise, not successful removal
}

主要方法：

public static void main(String[] args) {

   OrderedLinkedList list = new OrderedLinkedList();
   OrderedLinkedList removedList = new OrderedLinkedList();

   modCount = 0;
   list.add("Dog");
   list.add("Bird");
   list.add("dog");
   list.add("bird");
   list.add("Cat");
   System.out.println("Before removal of element");
   System.out.println(list);
   list.remove("Dog");
   removedList.add("Dog"); //not what I'm wanting to do
   System.out.println("Removed " + removedList);
   System.out.println("After removal of element");
   System.out.println(list);
   System.out.println("Total modifications = " + modCount);
   System.out.println();
}

输出：

Before removal of element
Bird, Cat, Dog, bird, dog
Removed Dog //not actually accessing the element originally removed. just printing a new list
After removal of element
Bird, Cat, bird, dog
Total modifications = 7 //unnecessary modification due to additional add

Answer 1

如果只想存储删除的元素而不增加修改次数，可以使用ArrayList并将删除的元素放入其中。这样您的修改次数就不会受到影响。

Answer 2

您可以通过实施额外的 pop 方法来存储删除的值。 return 类型应该是 Comparable 并且当找到要删除的对象时，将其存储在 temporary 对象和 return，而不是 returning boolean true。当找不到对象时，只需return null。

如果找到要删除的 Comparable 对象，该方法将 return 该对象以便您可以存储它。如果不是，则 null 将 return 以便您可以对 pop 方法使用 if-check 来获取如果删除是成功与否。

这是我刚刚为您编写的示例方法；

流行方法示例

public Comparable pop(Comparable obj) {

    for (OrderedListNode element = head.next; element != tail; element = element.next) {

        Comparable temp = null;     // declaration of the temporary object

        if (obj.equals(element.dataItem)) { // if element being removed is
                                            // at the cursor

            temp = obj;                     // store obj in temp

            OrderedListNode previousNode = element.before;
            OrderedListNode nextNode = element.next;

            nextNode.before = previousNode; // places next element that's
                                            // after before to the element
                                            // after current element [prev
                                            // -> current -> next]

            previousNode.next = nextNode;   // places prev of next element to
                                            // the element before current

            element.dataItem = (Comparable) NOT_FOUND;  // removed element is
                                                        // now null

            modCount++; // another modification
            theSize--; // reduce the size by 1

            return temp; // if remove is successful
        }
    }
    return null; // otherwise, not successful removal
}

测试演示

你的测试代码应该是这样的；

public static void main(String[] args) {

    OrderedLinkedList list = new OrderedLinkedList();
    OrderedLinkedList removedList = new OrderedLinkedList();

    modCount = 0;
    list.add("Dog");
    list.add("Bird");
    list.add("dog");
    list.add("bird");
    list.add("Cat");
    System.out.println("Before removal of element");
    System.out.println(list);

    // list.remove("Dog"); // not needed anymore
    // removedList.add("Dog"); //not what I'm wanting to do

    // pop returns the removed object
    removedList.add(list.pop("Dog"));

    System.out.println("Removed " + removedList);
    System.out.println("After removal of element");
    System.out.println(list);
    System.out.println("Total modifications = " + modCount);
    System.out.println();
}

如何在自定义 OrderedLinkedList class 中显示从列表中删除了哪些元素？

How can I display which elements were removed from list in custom OrderedLinkedList class?

java

data-structures

linked-list

doubly-linked-list

流行方法示例

测试演示