我意识到这是一个迟到的帖子，我提供的解决方案不是递归的，但这会从您的字符串中生成一个节点集合。为了使其递归，你需要的一切都应该在下面。
要创建递归算法，您必须首先确定您的基本情况是什么，然后只需创建一个条件来覆盖所有可能的子句。
在以下解决方案中，基本情况的一个示例是，字符串元素为 null 或为空，如果是，则返回结果。另一种选择是，前一个节点深度大于当前节点深度。如果是，则返回根节点并将当前节点分配为新根。根据您选择的解决方案将决定您如何获得最终结果。创建一个递归算法来完成这个任务可能是多余的，因为一个简单的循环和比较会让你得到相同的结果。无论您选择哪种方式，这都应该让您开始。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
namespace SampleTextParsing
{
class Program
{
/// <summary>
/// String representing the hierarchy to be parsed into objects.
/// </summary>
static readonly string fileString =
@"Item0
--Item1
----Property1
----Property2
----Item2
------Property1
------Property2
----Item3
----Item4
------Property1
------Property2
----Item5
--Item6
--Item7
----Property1
--End
End";
static void Main(string[] args)
{
// Create a collection of nodes out of the string.
Queue<BaseNode> nodes = Parse();
// Display the results to the user.
Console.WriteLine("Element string\r\n-------------------------------");
Console.WriteLine(fileString.Replace(' ', '\r'));
Console.WriteLine("\r\nTotals\r\n-------------------------------");
DisplayTotals(nodes);
Console.WriteLine("\r\nHierarchy\r\n-------------------------------");
while (nodes.Count > 0)
{
DisplayRelationships(nodes.Dequeue());
}
Console.ReadLine();
}
/// <summary>
/// Parses the hierarchy string into a collection of objects.
/// </summary>
/// <returns>A collection of BaseNode objects</returns>
static Queue<BaseNode> Parse()
{
BaseNode root = null; // Keeps track of the top most parent (Eg. In this case, item0 or End
BaseNode current = null; // Keeps track of the node to compare against.
BaseNode previous = null; // Keeps track of the previously seen node for comparison.
Queue<BaseNode> queue = new Queue<BaseNode>(); // Contains a queue of nodes to be returned as the result.
// Split the string into it's elements by using the carriage return and line feed.
// You can add a white-space character as a third delimiter just in case neither of the other two exist in the string. (eg. Inline)
string[] elements = fileString.Split(new char[] {'\n', '\r'}, StringSplitOptions.RemoveEmptyEntries);
// Iterate through every string element and create a node object out of it, while setting it's parent relationship to the previous node.
foreach (var element in elements)
{
// Check if a root node has been determined (eg. top most parent). If not, assign it as the root and set it as the current node.
if (root == null)
{
root = GetAsElementNode(element);
current = root;
}
// The root has already been determined and set as the current node. So now we check to see what it's relationship is to the
// previous node. (eg. Child to parent)
else
{
// Assign the current node as previous, so that we have something to compare against. (eg. Previous to Current)
previous = current;
// Create a node out of the string element.
current = GetAsElementNode(element);
// We use the depth (eg. integer representing how deep into the hierarchy we are, where 0 is the root, and 2 is the first child
// (This is determined by the number of dashes prefixing the element. eg. Item0 -> --Item1)) to determine the relationship.
// First, lets check to see if the previous node is the parent of the current node.
if (current.Depth > previous.Depth)
{
// It is, so assign the previous node as being the parent of the current node.
current.Parent = previous;
}
// The previous node is not the parent, so now lets check to see if the previous node is a sibling of the current node.
// (eg. Do they share the same parent?)
else if (current.Depth == previous.Depth)
{
// They do, so get the previous node's parent, and assign it as the current node's parent as well.
current.Parent = previous.Parent;
}
// The current node is not the parent (eg. lower hierarchy), nor is it the sibling (eg. same hierarchy) of the previous node.
// So it must be higher in the hierarchy. (eg. It's depth is less than the previous node's depth.)
else
{
// So now we must determine what the previous sibling node was and assign it as the current node's parent temporarily
BaseNode previousSibling = queue.FirstOrDefault(sibling => sibling.Depth == current.Depth);
current.Parent = previousSibling;
// The only time that the pervious sibling should be null is if the sibling is a root node. (eg. Item0 or End)
if (previousSibling == null)
{
current.Parent = null;
}
// The previous sibling has a parent, so we will the parent of the current node to match it's sibling.
else
{
current.Parent = previousSibling.Parent;
}
}
}
// We now add the node to the queue that will be returned as the result.
queue.Enqueue(current);
}
return queue;
}
/// <summary>
/// Simply outputs to console, the name of the node and it's relationship to the previous node if any.
/// </summary>
/// <param name="node">The node to output the name of.</param>
private static void DisplayRelationships(BaseNode node)
{
string output = string.Empty;
if (node.Parent == null)
{
output = string.Format("{0} is a root node.", node.Name);
}
else
{
output = string.Format("{0} is a child of {1}.", node.Name, node.Parent.Name);
}
Console.WriteLine(output);
}
/// <summary>
/// Displays the total counts of each relationship. The numbers appear slightly off because the clauses are not
/// taking into account that a root node has no parent but can have children. So Item0 and End are excluded from the count
/// but included in the root count. The values are right otherwise.
/// </summary>
/// <param name="nodes">A queue of nodes to iterate through.</param>
private static void DisplayTotals(Queue<BaseNode> nodes)
{
var totalRoot = nodes.Where(node => node.Parent == null).Count();
var totalChildren = nodes.Where(node => node.Parent != null).Count();
var totalChildless = nodes
.Where(node => node.Parent != null)
.Join(
nodes.Where(
node => (node.Parent != null)),
parent => parent.Name,
child => child.Parent.Name,
(parent, child) => new { child })
.Count();
Console.WriteLine("{0} root nodes.", totalRoot);
Console.WriteLine("{0} child nodes.", totalChildren);
Console.WriteLine("{0} nodes without children.", totalChildless);
Console.WriteLine("{0} parent nodes.", totalChildren - totalChildless);
}
/// <summary>
/// Creates a node object from it's string equivalent.
/// </summary>
/// <param name="element">The parsed string element from the hierarchy string.</param>
/// <returns></returns>
static BaseNode GetAsElementNode(string element)
{
// Use some regex to parse the starting portion of the string. You can also use substring to accomplish the same thing.
string elementName = Regex.Match(element, "[a-zA-Z0-9]+").Value;
string link = Regex.Match(element, "-+").Value;
// Return a new node with an element name and depth initialized.
return new Node(elementName, link.Length);
}
}
/// <summary>
/// A node object which inherits from BaseNode.
/// </summary>
public class Node : BaseNode
{
public Node()
{
}
/// <summary>
/// Overloaded constructor which accepts a string element and the depth
/// </summary>
/// <param name="elementName">The element as a string</param>
/// <param name="depth">The depth of the element determined by the number of dashes prefixing the element string.</param>
public Node(string elementName, int depth)
: base(elementName, depth)
{
}
}
/// <summary>
/// A base node which implements the INode interface.
/// </summary>
public abstract class BaseNode : INode
{
public string Name { get; set; } // The name of the node parsed from the string element.
public int Depth { get; set; } // The depth in the hierarchy determined by the number of dashes (eg. Item0 -> --Item1)
public BaseNode Parent { get; set; } // The parent of this node.
public BaseNode()
{
}
/// <summary>
/// Overloaded constructor which accepts a string element and the depth.
/// </summary>
/// <param name="elementName">The element as a string.</param>
/// <param name="depth">The depth of the element determined by the number of dashes prefixing the element string.</param>
public BaseNode(string elementName, int depth)
: this()
{
this.Name = elementName;
this.Depth = depth;
}
}
/// <summary>
/// The interface that is implemented by the BaseNode base class.
/// (For this scenario, this is a bit overkill but I figured, if I'm going to propose a solution, to do it right!)
/// </summary>
public interface INode
{
string Name { get; set; } // The name of the node parsed from the string element.
int Depth { get; set; } // The depth in the hierarchy determined by the number of dashes (eg. Item0 -> --Item1)
BaseNode Parent { get; set; } // The parent of this node.
}
}
输出如下：
Element string
-------------------------------
Item0
--Item1
----Property1
----Property2
----Item2
------Property1
------Property2
----Item3
----Item4
------Property1
------Property2
----Item5
--Item6
--Item7
----Property1
--End
End
Totals
-------------------------------
2 root nodes.
15 child nodes.
11 nodes without children.
4 parent nodes.
Hierarchy
-------------------------------
Item0 is a root node.
Item1 is a child of Item0.
Property1 is a child of Item1.
Property2 is a child of Item1.
Item2 is a child of Item1.
Property1 is a child of Item2.
Property2 is a child of Item2.
Item3 is a child of Item1.
Item4 is a child of Item1.
Property1 is a child of Item4.
Property2 is a child of Item4.
Item5 is a child of Item1.
Item6 is a child of Item0.
Item7 is a child of Item0.
Property1 is a child of Item7.
End is a child of Item0.
End is a root node.