如何建立和/或树？ [英] How to build an and-or tree?

问题描述

我需要一个支持和和或的树结构。例如，给定一个正常的表达式，如 ab | c（d | e）我想把它变成树。

因此，起初我们有两个或分支，可以下降 ab 或 c（d | e） 。如果您朝下 ab 分支，您将得到两个节点， a 和 b （或 a ，后跟 b ，无论如何）。然后，如果您沿着 c（d | e）分支，您将获得 c 和 （d | e），然后（d | e）被拆分为 d 或 e 。

使树结构很简单你只需要一些类似

  class Node {
 string element; 
 Node [] children; 
} 
  

但是，你怎么知道孩子是否应该和 ？我猜每个级别的树应该在和和oring之间交替

有意义吗？任何人都可以为此建议一个结构？

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有几个人建议在节点上存储运算符，即好的，但是没有办法利用每个级别总是交替的事实，或者，或者，和...？

编辑：不太确定为什么人们认为这是二叉树。 不是。我希望这个微小的代码段可以让你失望。

---

目前倾向于：

 抽象类Node {} 
 
 class DataNode：Node 
 {
 string data ; 
} 
 
抽象类OpNode：Node 
 {
 Node [] children; 
} 
 
 class OrNode：OpNode {} 
 class AndNode：OpNode {} 
  

解决方案

想想一个树结构，其中每个节点都表示一个布尔表达式，可以被评估为true或false - 在您的情况下，正则表达式（匹配或不匹配）。
树结构本身表示AND和OR：
每个路由，从根节点开始，以不再有子节点的结点结束，表示为AND的表达式。
树

  A 
 / 
 B 
 / 
 C 
  

将代表A AND B AND C。

每当一个节点有多个子节点时，有一个OR（分离），分支到几个路由：

  A 
 / \ 
 BD 
 / 
 C 
  

表示A AND（（B AND C）或D）

所以你甚至不需要在任何地方存储运营商。

在您的示例中，您的表达式为 ab | c（d | e），因此没有常见的根表达式进行评估;我建议在这种情况下，根本就是简单的 true ，树将如下所示：

  true 
 / \ 
 AC 
 / / \ 
 BDE 
  

对于c＃中的自定义树类，请查看树数据C＃中的结构，或搜索或制作自己的一个。

I need a tree structure that supports "and" and "or"ing. For example, given a regular expression like ab|c(d|e) I want to turn that into a tree.

So, at first we have two "or" branches... it can either go down ab, or c(d|e). If you head down the ab branch, you get two nodes, a and b (or a followed by b, whatever). Then if you go down the c(d|e) branch, you get c and (d|e), then (d|e) is split into d or e.

Making a tree structure is easy, you just have something like

class Node {
    string element;
    Node[] children;
}

But then how do you know if the children should be "anded" or "ored"? I guess each level of the tree should alternate between "anding" and "oring"

Does that make sense? Can anyone suggest a structure for this?

---

A few people have suggested storing the "operator" on the node, which is fine, but isn't there a way to take advantage of the fact that each level always alternates or,and,or,and,...?

Edit: Not quite sure why people keep assuming this is a binary tree. It's not. I was hoping the tiny code snippet would tip you off. The example just happens to have only 2 branches.

---

Currently leaning towards this:

abstract class Node { }

class DataNode : Node
{
    string data;
}

abstract class OpNode : Node
{
    Node[] children;
}

class OrNode : OpNode { }
class AndNode : OpNode { }

解决方案

Think of a tree structure where every node represents a boolean expression that can be evaluated to be either true or false - in your case a regular expression (match or non-match). The tree structure itself represents AND and OR: Each route, starting at the root node and ending with a node that has no further children, is a conjunction of expressions, representing AND. The tree

    A
   /
  B
 /
C

would represent A AND B AND C.

Whenever a node has more than 1 child node, there is an OR (disjunction), branching into several routes:

    A
   / \
  B   D
 /
C

represents A AND ((B AND C) OR D)

So you do not even need to store the operators anywhere.

In your example you have the expression ab|c(d|e) so there is no common root expression to evaluate; I suggest the root in this case is simply true and the tree would look like:

   true
   / \
  A   C
 /   / \
B   D   E

For a custom tree class in c# look here Tree data structure in C# or search on or make one of your own.

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