在枚举时插入队列 [英] inserting into a queue while enumerating it

问题描述

我想使用队列对树进行广泛的首次搜索

I want to do a breadth first search of a tree using a Queue

var q = new Queue<T>();

q.Enqueue(Root);

foreach(T root in q)
{
  foreach(T t in root.Children)
    q.Enqueue(t);
}

然而，我得到一个在枚举器被实例化之后被修改的集合。

However I get a "Collection was modified after the enumerator was instantiated." Exception.

有没有C＃类型，我可以这样做？

Is there a C# type that I can do this with?

编辑：一点点阅读让我的东西，我可能会这样做完全错误。

a little reading make me thing I might be doing this totally wrong.

有没有办法使用foreach从队列中排队？

Is there a way to use a foreach to dequeue from a Queue?

这样做是丑的（OMHO）

this works but is ugly (OMHO)

var q = new Queue<T>();

q.Enqueue(Root);

while(q.Count > 0)
{
  T root = q.Dequeue();
  foreach(T t in root.Children)
    q.Enqueue(t);
}

推荐答案

你不能枚举过一个IEnumerable并同时更改相同的IEnumerable。我不认为有一个C＃集合将允许这个。

You can't enumerate over an IEnumerable and change the same IEnumerable at the same time. I don't think there is a C# Collection that will allow this.

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