怎样才能增加一个链表＆LT; T＆GT;要在LinkedList＆LT; T＆GT;在C＃中？ [英] How does one add a LinkedList<T> to a LinkedList<T> in C#?

问题描述

有人会认为简单的code

One would think the simple code

llist1.Last.Next = llist2.First;
llist2.First.Previous = llist1.Last;

会的工作，但显然在C＃中的链表，首先，最后，和它们的性质只能得到。

would work, however apparently in C#'s LinkedList, First, Last, and their properties are Get only.

另一种方法是我能想到的就是

The other method I could think of was

llist1.AddLast(llist2.First);

不过，这也不行 - 它失败，因为llist2的第一个节点已经在链表

However, this does not work either - it fails because the first node of llist2 is already in a linked list.

这是否意味着，我必须有一个循环，手动llist2的AddLast的每个节点llist1？这难道不是打败链表????效率

Does this mean that I have to have a loop that manually AddLast's each node of llist2 to llist1? Doesn't this defeat the efficiency of linked lists????

推荐答案

是的，你必须循环，很遗憾。这是一个O（n）的操作 - O（1）为每个条目添加。还有的需要一个缓冲的风险调整大小和复制等 - 当然，虽然垃圾收集可能会做粗略的:)你甚至可以写一个方便的扩展方法：

Yes, you have to loop, unfortunately. This is an O(n) operation - O(1) for each entry added. There's no risk of requiring a buffer to be resized and copied, etc - although of course garbage collection might do roughly that :) You could even write handy extension methods:

public static class LinkedListExtensions   
{
    public static void AppendRange<T>(this LinkedList<T> source,
                                      IEnumerable<T> items)
    {
        foreach (T item in items)
        {
            source.AddLast(item);
        }
    }

    public static void PrependRange<T>(this LinkedList<T> source,
                                       IEnumerable<T> items)
    {
        LinkedListNode<T> first = source.First;
        foreach (T item in items)
        {
            source.AddBefore(first, item);
        }
    }
}

编辑：埃里希的意见建议，为什么你可能会认为这是低效的 - 为什么不加入我们的两个列表一起通过更新第一列表的尾部和preV的下一个指针头指针的第二？嗯，想想会发生什么样的第二列表... 是的会随之改变。

不仅如此，但会发生什么这些节点的所有权？每个本质上是两个列表的一部分，现在...但一个LinkedListNode＆LT; T＆GT;的.List 属性只能说服他们约一

Not only that, but what would happen to the ownership of those nodes? Each is essentially part of two lists now... but the LinkedListNode<T>.List property can only talk about one of them.

虽然我能明白你为什么会想这样做在某些情况下，该方式使.NET 的LinkedList＆LT; T＆GT; 类型已建成基本禁止它。我觉得这个文档注释中解释说得好：

While I can see why you might want to do this in some cases, the way that the .NET LinkedList<T> type has been built basically prohibits it. I think this doc comment explains it best:

在的LinkedList＆LT; T＆GT;）类做   不支持链接，分裂，   周期，或其它功能，可以   离开不一致名单   状态。

The LinkedList<T>) class does not support chaining, splitting, cycles, or other features that can leave the list in an inconsistent state.

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