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read csv file and return indented menu c#

I have to create an indented navigation menu using below data from a .csv file:
ID;MenuName;ParentID;isHidden;LinkURL1;Company;NULL;False;/company2;About Us;1;False;/company/aboutus3;Mission;1;False;/company/mission4;Team;2;False;/company/aboutus/team5;Client 2;10;False;/references/client26;Client 1;10;False;/references/client17;Client 4;10;True;/references/client48;Client 5;10;True;/references/client510;References;NULL;False;/references
Using this data I have to develop an application that will parse the file and present the content in a console as the example below:
. Company.... About Us....... Team.... Mission. References.... Client 1.... Client 2
Menu items should be indented (depending on the parent), hidden items (isHidden==true) shouldn't be presented and items should be ordered alphabetically. So far I tried:
using (StreamReader sr = new StreamReader(#"file.csv"))
{
// Read the stream to a string, and write the string to the console.
string [] lines = sr.ReadToEnd().Split(/*';', */'\n');
for (int i = 1; i < lines.Length; i++)
{
Console.WriteLine($"String no {i} is : {lines[i-1]}");
}
}
With this i'm getting the lines but I'm stuck after that. I'm new in coding so any help will be appreciated :)

heres some code that should help you get off.
Working sample:
https://dotnetfiddle.net/L37Gjr
It first parses the data to a seperate object. This then gets used to build a m-ary tree, or a hierachical structure of connected nodes. (a node has a reference to 0 or more children).
https://en.wikipedia.org/wiki/M-ary_tree
Then tree traversal (use google if you need to know more) is used to insert and print the output, There is still something wrong however. it now uses level order traversal to print, this however comes up with an error:
Found root:1 - Company
Found root:10 - References
-------------------
1 - Company
2 - About Us
3 - Mission
4 - Team
10 - References
6 - Client 1
5 - Client 2
As you can see, it prints 4 - Team on the wrong level. I'll leave it to you to fix it (because i ran out of time), and if not i hope i gave you plenty ideas to go off and research on your own.
// sample for https://stackoverflow.com/questions/61395486/read-csv-file-and-return-indented-menu-c-sharp by sommmen
using System;
using System.Collections;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public class Node<T>
{
public T Data {get;set;}
public List<Node<T>> Children { get; set;}
public Node()
{
Children = new List<Node<T>>();
}
// Tree traversal in level order
public List<Node<T>> LevelOrder()
{
List<Node<T>> list = new List<Node<T>>();
Queue<Node<T>> queue = new Queue<Node<T>>();
queue.Enqueue(this);
while(queue.Count != 0)
{
Node<T> temp = queue.Dequeue();
foreach (Node<T> child in temp.Children)
queue.Enqueue(child);
list.Add(temp);
}
return list;
}
public List<Node<T>> PreOrder()
{
List<Node<T>> list = new List<Node<T>>();
list.Add(this);
foreach (Node<T> child in Children)
list.AddRange(child.PreOrder());
return list;
}
public List<Node<T>> PostOrder()
{
List<Node<T>> list = new List<Node<T>>();
foreach (Node<T> child in Children)
list.AddRange(child.PreOrder());
list.Add(this);
return list;
}
}
public class Entity
{
public int id {get;set;}
public string menuName {get;set;}
public int? parentID {get;set;}
public bool isHidden {get;set;}
public string linkURL {get;set;}
}
public static void Main()
{
var data = #"ID;MenuName;ParentID;isHidden;LinkURL
1;Company;NULL;False;/company
2;About Us;1;False;/company/aboutus
3;Mission;1;False;/company/mission
4;Team;2;False;/company/aboutus/team
5;Client 2;10;False;/references/client2
6;Client 1;10;False;/references/client1
7;Client 4;10;True;/references/client4
8;Client 5;10;True;/references/client5
10;References;NULL;False;/references";
var lines = data.Split('\n');
var rootNodes = new List<Node<Entity>>();
var childItems = new List<Entity>();
// Parse the data to entities
// Items without a parent are used as rootnodes to build a tree
foreach(var row in lines.Skip(1))
{
var columns = row.Split(';');
var id = Convert.ToInt32(columns[0]);
var menuName = columns[1];
var parentID = ToNullableInt(columns[2]);
var isHidden = Convert.ToBoolean(columns[3]);
var linkURL = columns[4];
var entity = new Entity()
{
id = id,
menuName = menuName,
parentID = parentID,
isHidden = isHidden,
linkURL = linkURL
};
if(parentID == null)
{
Console.WriteLine("Found root:" + entity.id + " - " + entity.menuName);
rootNodes.Add(new Node<Entity>()
{
Data = entity
});
}
else
{
childItems.Add(entity);
}
}
// Add the childElements to their appropriate rootnode
foreach(var rootNode in rootNodes)
{
foreach(var childItem in childItems.OrderBy(a=>a.parentID).ThenBy(b=>b.menuName))
{
var newNode = new Node<Entity>()
{
Data = childItem
};
Insert(rootNode, newNode);
}
}
Console.WriteLine("-------------------");
foreach(var rootNode in rootNodes)
{
var indent = 0;
var previous = rootNode;
foreach(var node in rootNode.LevelOrder())
{
if(node.Data.isHidden) continue;
if(previous.Data.parentID != node.Data.parentID)
indent++;
for(var i = 0; i < indent; i++)
Console.Write("\t");
Console.WriteLine(node.Data.id + " - " + node.Data.menuName);
previous = node;
}
}
}
public static void Insert(Node<Entity> rootNode, Node<Entity> targetNode)
{
foreach(var current in rootNode.LevelOrder())
{
if(current.Data.id == targetNode.Data.parentID)
{
current.Children.Add(targetNode);
return;
}
}
}
public static int? ToNullableInt(string s)
{
int i;
if (int.TryParse(s, out i)) return i;
return null;
}
}

C# How to pool the objects of a node tree efficiently?

I have a node class that contains only value type properties, and one reference type: it's parent node. When performing tree searches, these nodes are created and destroyed hundreds of thousands of times in a very short time span.
public class Node
{
public Node Parent { get; set; }
public int A { get; set; }
public int B { get; set; }
public int C { get; set; }
public int D { get; set; }
}
The tree search looks something like this:
public static Node GetDepthFirstBest(this ITree tree, Node root)
{
Node bestNode = root;
float bestScore = tree.Evaluate(root);
var stack = new Stack<Node>();
stack.Push(root);
while(stack.Count > 0)
{
var current = stack.Pop();
float score = tree.Evaluate(current);
if (score > bestScore)
{
bestNode = current;
bestScore = score;
}
var children = tree.GetChildren(current);
foreach(var c in children) { stack.Push(c); }
}
return bestNode;
}
Because this is done in a Mono runtime that has a very old GC, I wanted to try and pool the node objects. However, I am at a loss on how to know when a node object is safe to return to the pool, since other nodes that are still in use might reference it as a parent. At the end of the search, the best node is returned and a list of nodes is formed by walking back through its ancestors. I have full control over how the nodes are created inside the tree, if that's useful.
What options could I try and implement?

So, fortunately, if you're doing a Depth-First-Search, which you appear to be, this is a bit easier. Any time you reach a leaf node, there are two possibilities: that leaf node is part of the current deepest tree, or it's not.
If it's not, that means it's safe to return this node to the pool. If it is, that means we can return any nodes in our old tree back to our pool that are not in our own ancestor chain.
Now, if we're not a leafnode, we don't know if we can be freed until after we've finished checking our children. then, once all our children are checked, we find out if any of our children said they were the current best. if so, we keep ourselves
this does mean we're doing quite a bit more checking.
Here's some sudo code:
List bestNodes;
bool evalNode(node, score)
{
if (childCount == 0)
{
if (score > bestScore)
{
bestScore = score;
bestNode = node;
bestNodes.Add(node);
return true;
}
else
{
freeNode(this);
return false;
}
}
else
{
bool inLongest = false;
foreach (child in children)
{
inLongest = evalNode(child, score + 1) || inLongest;
}
if (!inLongest)
{
freeNode(node);
}
else
{
free(bestNodes[score]);
bestNodes[score] = node;
}
return inLongest;
}
}

Try using the ref keyword if your node is a struct, this avoids copying the node every time you pass it through to a function.
Thus:
struct Node
{
object obj;
Node children;
}
public void DoStuffWithNode(ref Node pNode){...Logic...}

Creating a Treeview recursively

I want to create a treeview in c# which will group file by prefix (here the prefix is a marked by the separator _). The following files should give this tree:
Files list :
p_a
p_a_test
p_LIG
p_p
p_p_c
p_p_c2
p_p_ccc
p_p_test
p_tres
TestLineGraph1
TestLineGrpah
Corresponding tree:
|--p_
|--p_a
|--p_a_test
|--p_LIG
|--p_p
|--p_p_
|--p_p_c
|--p_p_c2
|--p_p_ccc
|--p_p_test
|--p_tres
TestLineGraph1
TestLineGrpah
Here's my attempt of code:
private GraphUINode(List<string> subNodes, GraphUINode parent, string name, int lvl = 0)
: base(parent.m_viewDataSubControl)
{
parent.Nodes.Add(this);
this.Name = name;
this.Text = name;
string currentPrefix = "";
int pertinentSubNodes = 0;
while (pertinentSubNodes < subNodes.Count -1 && subNodes[pertinentSubNodes].Split('_').Length < 2+ lvl)
pertinentSubNodes++;
for (int i = 0; i <= lvl; i++)
{
currentPrefix += subNodes[pertinentSubNodes].Split('_')[i] + "_";
}
List<String> children = new List<string>();
foreach (string child in subNodes)
{
// The child is in the same group than the previous one
if (child.StartsWith(currentPrefix))
{
children.Add(child);
}
else
{
// Create a node only if needed
if (children.Count > 1)
{
// Create the new node
new GraphUINode(children, this, currentPrefix, lvl + 1);
children.Clear();
children.Add(child);
}
else
{
new GraphTemplateNode(this, m_viewDataSubControl, child);
}
currentPrefix = "";
for (int i = 0; i <= lvl; i++)
{
currentPrefix += child.Split('_')[i] + "_";
}
}
}
}
But I miss a few ones in the final result:
How can I get its back? Even when I debug step by step I can't find the logical way to do it.

So the first thing that we'll want to do here is take our strings and turn them into a tree. Once we have a tree then mapping those nodes to a TreeView is quite easy.
We'll start out with the definition for the tree itself:
public class Node<T>
{
public Node(T value, IEnumerable<Node<T>> children)
{
Value = value;
Children = children;
}
public T Value { get; private set; }
public IEnumerable<Node<T>> Children { get; private set; }
}
Nice and easy, each node is just a value and a collection of children.
Next we'll write a method to take a sequence of sequences, and build a tree from it. The idea here is that we'll group all of the items based on the first value in their sequence, build a node for each group, and then recursively call the method on the group to get the children for that node.
public static IList<Node<T>> GroupToTree<T>(this IEnumerable<IEnumerable<T>> source)
{
return GroupToTree(source.Select(sequence => sequence.GetEnumerator()));
}
private static IList<Node<T>> GroupToTree<T>(IEnumerable<IEnumerator<T>> source)
{
return source.WhereHasNext()
.GroupBy(iterator => iterator.Current)
.Select(group => new Node<T>(group.Key, GroupToTree(group)))
.ToList();
}
//This ensures that the iterators all get disposed
private static IEnumerable<IEnumerator<T>> WhereHasNext<T>(
this IEnumerable<IEnumerator<T>> source)
{
foreach (var iterator in source)
{
if (iterator.MoveNext())
yield return iterator;
else
iterator.Dispose();
}
}
Now we can take the raw data, split each of the strings into sequences of strings, and then map each of the nodes that we have here into UI-based nodes for presentation:
List<string> rawData = new List<string>();
//TODO populate raw data
Func<Node<string>, TreeNode> selector = null;
selector = node => new TreeNode(node.Value, node.Children.Select(selector).ToArray());
var nodes = rawData.Select(line => line.Split('_').AsEnumerable())
.GroupToTree()
.Select(selector);

Loop detection in LinkedList using C#

In the interview question, "Implement an algorithm which detects for presence of the loop.". For example, the linked list has a loop, like:
0--->1---->2---->3---->4---->5---->6
▲ |
| ▼
11<—-22<—-12<—-9<—-8
Using Floyd's cycle detection, this problem can be solved by using a fast & slow pointer. So should I try comparing
a. Link's node values, i.e.
if (fast.data == slow.data)
break;
where fast and slow are of type Link
class Link
{
int IData {get; set;}
Link Next {get; set;}
}
OR
b. Are they pointing to same reference, i.e. if (fast == slow)
Thanks.

You should only be comparing the nodes themselves. After all, it's reasonable to have a linked list with repeated data in, without it actually having a cycle.
I would call them nodes rather than links too. A link is simply the reference from one node to the next or previous one - in particular, there's no data associated with a link, only with a node.

Hope this helps... It might be naive but it works...
using System;
namespace CSharpTestTemplates
{
class LinkedList
{
Node Head;
public class Node
{
public int value;
public Node NextNode;
public Node(int value)
{
this.value = value;
}
}
public LinkedList(Node head)
{
this.Head = head;
}
public Boolean hasLoop()
{
Node tempNode = Head;
Node tempNode1 = Head.NextNode;
while(tempNode!=null && tempNode1!=null){
if(tempNode.Equals(tempNode1)){
return true;
}
if ((tempNode1.NextNode != null) && (tempNode.NextNode != null))
{
tempNode1 = tempNode1.NextNode.NextNode;
tempNode = tempNode.NextNode;
}
else
{
return false;
}
}
return false;
}
public static void Main()
{
Node head = new Node(1);
LinkedList ll = new LinkedList(head);
Node node2 = new Node(2);
Node node3 = new Node(3);
Node node4 = new Node(4);
Node node5 = new Node(5);
Node node6 = new Node(6);
head.NextNode = node2;
node2.NextNode = node3;
node3.NextNode = node4;
node4.NextNode = node5;
node5.NextNode = node6;
node6.NextNode = null;
Console.WriteLine(ll.hasLoop());
Console.Read();
}
}
}

Recursive LINQ calls

I'm trying to build an XML tree of some data with a parent child relationship, but in the same table.
The two fields of importance are
CompetitionID
ParentCompetitionID
Some data might be
CompetitionID=1,
ParentCompetitionID=null
CompetitionID=2,
ParentCompetitionID=1
CompetitionID=3,
ParentCompetitionID=1
The broken query I have simply displays results in a flat format. Seeing that I'm working with XML, some sort of recursive functionality is required. I can do this using normal for loop recursion, but would like to see the linq version. Any help appreciated.
var results =
from c1 in comps
select new {
c.CompetitionID,
SubComps=
from sc in comps.Where (c2 => c2.CompetitionID == c1.CompetitionID)
select sc
};
Update
I found an interesting article by Chris Eargle here that shows you how to call lambda delegates recursively. Here is the code. Thanks Chris!
Func<int, int> factoral = x => x <= 1 ? 1 : x + factoral(--x);
Func<int, int> factoral = null;
factoral = x => x <= 1 ? 1 : x + factoral(--x);
^ added code formatting to show the lamba funcs
The trick is to assign null to the Func delegate first.

Don't know how to write a recursive LINQ. But I think no recursion is actually required here. A tree may be built in just two steps:
Dictionary<int, Competition> dic = comps.ToDictionary(e => e.CompetitionID);
foreach (var c in comps)
if (dic.ContainsKey(c.ParentCompetitionID))
dic[c.ParentCompetitionID].Children.Add(c);
var root = dic[1];
The root variable now contains the complete tree.
Here's a complete sample to test:
using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApplication2
{
class Competition
{
public int CompetitionID;
public int ParentCompetitionID;
public List<Competition> Children=new List<Competition>();
public Competition(int id, int parent_id)
{
CompetitionID = id;
ParentCompetitionID = parent_id;
}
}
class Program
{
static void Main(string[] args)
{
List<Competition> comps = new List<Competition>()
{
new Competition(1, 0),
new Competition(2,1),
new Competition(3,1),
new Competition(4,2),
new Competition(5,3)
};
Dictionary<int, Competition> dic = comps.ToDictionary(e => e.CompetitionID);
foreach (var c in comps)
if (dic.ContainsKey(c.ParentCompetitionID))
dic[c.ParentCompetitionID].Children.Add(c);
var root = dic[1];
}
}
}

I know I'm a little too late here. But you said you already had a version using foreach :) So if it should actually be recursive and use linq this would be a solution:
internal class Competition
{
public int CompetitionID;
public int ParentCompetitionID;
public Competition(int id, int parentId)
{
CompetitionID = id;
ParentCompetitionID = parentId;
}
}
internal class Node
{
public Node(int id, IEnumerable<Node> children)
{
Children = children;
Id = id;
}
public IEnumerable<Node> Children { get; private set; }
public int Id { get; private set; }
}
internal class Program
{
static void Main(string[] args)
{
var comps = new List<Competition>
{
new Competition(1, 0),
new Competition(2, 1),
new Competition(3, 1),
new Competition(4, 2),
new Competition(5, 3)
};
Node root = ToTree(0, comps);
}
static readonly Func<int, IEnumerable<Competition>, Node> ToTree =
(nodeId, competitions) => new Node(nodeId, from c in competitions where c.ParentCompetitionID == nodeId select ToTree(c.CompetitionID, competitions));
}

You can get a tree like structure, combining LINQ and recursion with delegates. In this example I use a XML structure like this:
<Competitions>
<Competition ID="1" />
<Competition ID="2" ParentCompetitionID="1" />
<Competition ID="3" ParentCompetitionID="1" />
<Competition ID="4" />
</Competitions>
So to store node data in code and facilitate navigation, create a class like this:
class Competition
{
public int CompetitionID { get; set; }
public IEnumerable<Competition> Childs { get; set; }
}
Now using Linq to XML you load the xml file into an XDocument. After that declare a delegate that iterates over all the xml elements inside the document selecting nodes that have an id mathing the delegate's id paremeter. When selecting each node, it calls to the delegate again, passing the id of the parent node to look for. It first starts with the id parameter set to null, so, selecting firts the root nodes:
var doc = XDocument.Load("tree.xml");
//Declare the delegate for using it recursively
Func<int?, IEnumerable<Competition>> selectCompetitions = null;
selectCompetitions = (int? id) =>
{
return doc.Elements("Competitions").Elements().Where(c =>
{
//If id is null return only root nodes (without ParentCompetitionID attribute)
if (id == null)
return c.Attribute("ParentCompetitionID") == null;
else
//If id has value, look for nodes with that parent id
return c.Attribute("ParentCompetitionID") != null &&
c.Attribute("ParentCompetitionID").Value == id.Value.ToString();
}).Select(x => new Competition()
{
CompetitionID = Convert.ToInt32(x.Attribute("ID").Value),
//Always look for childs with this node id, call again to this
//delegate with the corresponding ID
Childs = selectCompetitions(Convert.ToInt32(x.Attribute("ID").Value))
});
};
var competitions = selectCompetitions(null);
To test it you can do a simply recurring method that prints the tree to the console:
private static void Write(IEnumerable<Competition> competitions, int indent)
{
foreach (var c in competitions)
{
string line = String.Empty;
for (int i = 0; i < indent; i++)
{
line += "\t";
}
line += "CompetitionID = " + c.CompetitionID.ToString();
Console.WriteLine(line);
if (c.Childs != null && c.Childs.Count() > 0)
{
int id = indent + 1;
Write(c.Childs, id);
}
}
}
Hope it helps!

I've done something very similar using LINQ's group by
I don't use the query syntax of LINQ, so forgive me if this is wrong:
var results = from c in comps
group c by c.ParentCompetitionID into g
select new { ParentId = g.Key, ChildId = g };
Of course, this would be better if your classes looked something like:
class Competition {
int Id;
string Description;
Competition ParentCompetition;
}
Then, instead of grouping by ID only, you can group by the entire competition, which makes generating the XML faster and easier.
var results = from c in comps
group c by c.ParentCompetition into g
select new { Parent = g.Key, Child = g };

class Competition
{
int ID { get; set;}
int ParentID { get; set; }
IEnumerable<Competition> Children { get; set; }
}
public IEnumerable<Competition> GetChildren(
IEnumerable<Competition> competitions, int parentID)
{
IEnumerable<Competition> children =
competitions.Where(c => c.ParentID == parentID);
if (children.Count() == 0)
return null;
return children.Select(
c => new Competition { ID = c.ID, Children = GetChildren(c.ID) };
}
Then you can just call GetChildren, passing the ID of the root as the parentID, and that will return a tree structure. You can also change the Competition object to the XML API of your choice.
I know this isn't exactly what you're looking for, but afaik LINQ doesn't support recursion. Nevertheless, the LIN part of LINQ means language integrated, which is exactly what I used.

While you can not do this with a single query (unless you are calling SQL directly with a CTE), you can limit the number of queries to the depth of the tree.
The code is too long to paste, but the basic steps are:
Collect root nodes and add to 'all' nodes
Collect nodes with parent in 'all' nodes (pass list to query)
Add nodes in step 2 to 'all' nodes
Repeat 2 - 3 till step 2 returns 0 nodes (which should be depth of tree + 1, I think).
You can minimize the amount of nodes passed to the query in step 2. SQL server tends to bomb out with a list of more than 2000 entries. (SQL Compact has no such issue though).