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Question:

I am working on a multi-level marketing (binary) which looks like this:

(but the binary tree is not required to be perfect. A node can have 0-2 child)

enter image description here

My problem is the data that I fetch from the database is flat list.enter image description hereenter image description here

Notice that I am using hierarchyid (sql server 2014)

Basically the TextNode column is like a breadcrumb.

every slash / represents a level.

If I have TextNode of /1/ as root. then every node that starts with /1/ belongs to that root which are /1/, /1/1/ and /1/1/1/ (the root node is included which will be the level 0)

I've tried the accepted answer in this question but its not working.

How can I transform the flatlist to a Binary Tree so that I can easily traverse and display it on a screen?

Im using C#, ASP MVC 5, SQL Server 2014 if it matters.


Best Answer:


Here is a very simple implementation (assuming that Nodes are in the right order), which may be enhanced in multiple ways

public interface IRow<out T>
{
    string TextNode { get; }
    T Value { get; }
}
public class TreeNode<T>
{
    private struct NodeDescriptor
    {
        public int Level { get; }
        public int ParentIndex { get; }
        public NodeDescriptor(IRow<T> row)
        {
            var split = row.TextNode.Split(new [] {"/"}, StringSplitOptions.RemoveEmptyEntries);
            Level = split.Length;
            ParentIndex = split.Length > 1 ? int.Parse(split[split.Length - 2]) - 1 : 0;
        }
    }
    public T Value { get; }
    public List<TreeNode<T>> Descendants { get; }
    private TreeNode(T value)
    {
        Value = value;
        Descendants = new List<TreeNode<T>>();
    }
    public static TreeNode<T> Parse(IReadOnlyList<IRow<T>> rows)
    {
        if (rows.Count == 0)
            return null;
        var result = new TreeNode<T>(rows[0].Value);
        FillParents(new[] {result}, rows, 1, 1);
        return result;
    }
    private static void FillParents(IList<TreeNode<T>> parents, IReadOnlyList<IRow<T>> rows, int index, int currentLevel)
    {
        var result = new List<TreeNode<T>>();
        for (int i = index; i < rows.Count; i++)
        {
            var descriptor = new NodeDescriptor(rows[i]);
            if (descriptor.Level != currentLevel)
            {
                FillParents(result, rows, i, descriptor.Level);
                return;
            }
            var treeNode = new TreeNode<T>(rows[i].Value);
            parents[descriptor.ParentIndex].Descendants.Add(treeNode);
            result.Add(treeNode);
        }
    }
}

Sample usage:

public class Row : IRow<string>
{
    public string TextNode { get; }
    public string Value { get; }
    public Row(string textNode, string userName)
    {
        TextNode = textNode;
        Value = userName;
    }
}
class Program
{
    static void Main(string[] args)
    {
        IRow<string>[] rows =
        {
            new Row("/", "Ahmed"),
            new Row("/1/", "Saeed"),
            new Row("/2/", "Amjid"),
            new Row("/1/1/", "Noura"),
            new Row("/2/1/", "Noura01"),
            new Row("/2/2/", "Reem01"),
            new Row("/1/1/1", "Under_noura")
        };
        var tree = TreeNode<string>.Parse(rows);
        PrintTree(tree);
    }
    private static void PrintTree<T>(TreeNode<T> tree, int level = 0)
    {
        string prefix = new string('-', level*2);
        Console.WriteLine("{0}{1}", prefix, tree.Value);
        foreach (var node in tree.Descendants)
        {
            PrintTree(node, level + 1);
        }
    }
}



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