[英]Recursion in C# iterator
Is it possible to use recursion in an iterator implementing System.Collections.IEnumerable
? 是否可以在实现System.Collections.IEnumerable
的迭代器中使用递归? I have a tree structure declared roughly like this: 我有一个大致像这样声明的树结构:
public class Node
{
public Node Sibling;
public Node Child;
}
I would like to iterate over the nodes in a tree. 我想迭代树中的节点。 I would like to do something like this (pseudocode, I guess this won't compile): 我想做这样的事情(伪代码,我猜这不会编译):
public class NodeIterator : System.Collections.IEnumerable
{
Node m_root;
public System.Collections.IEnumerator GetEnumerator()
{
recursiveYield(m_root);
}
System.Collections.IEnumeraton recursiveYield(Node node)
{
yield return node;
if (node.Child)
{
recursiveYield(node.Child);
}
if (node.Sibling)
{
recursiveYield(node.Sibling);
}
}
}
Is this somehow possible? 这有点可能吗? I realise this can be solved without recursion using a Node
deque in the GetEnumerator
function. 我意识到这可以使用GetEnumerator
函数中的Node
deque在没有递归的情况下解决。
Yes, all you need is to iterate the return value from the call site. 是的,您只需要从调用站点迭代返回值。 Like so: 像这样:
IEnumerable<T> Recursive(Node node)
{
yield return node;
foreach (var siblingNode in Recursive(node.Sibling))
{
yield return siblingNode;
}
foreach (var childNode in Recursive(node.Child))
{
yield return childNode;
}
}
For the record, this isn't better than using a queue to achieve eg breadth-first traversal. 对于记录,这并不比使用队列实现例如广度优先遍历更好。 The memory requirement for something like this is identical in the worst case. 在最坏的情况下,类似这样的内存需求是相同的。
不,因为recursiveYield(Node node)
函数将返回一个集合,您只能生成一个项目
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