Question

I’m searching for an algorithm which will convert a data structure like the following one, where each level is separated by a dot:

child1
child1.child9
child4.child10.child11
child4.child10.child12

into a valid HTML hierarchical list element like this:

<ul>
<li>child1
    <ul><li>child9</li></ul></li>
<li>child4
    <ul><li>child10
        <ul><li>child11</li><li>child12</li></ul></li></ul></li>
</ul>

Any suggestions?

Update

Problem
from this kind of structure(below) is easy to build hierarchical list

child
child.child1
child.child2
child.child2.child3

but my structure is

child.child2.child3
child7
child10.child14.child15
child10.child14.child16

so i dont have separate row to build parent element 🙁 i must build tree from one row if there is no parent

Answer 1

You could turn the list into a matrix and then use grouping/recursion. Here’s an example. It doesn’t pretty print the HTML, but it should give the correct result.

    static void Main(string[] args)
    {
        var list = new List<String>()
        {
            "child.child2.child3",
            "child7",
            "child10.child14.child15",
            "child10.child14.child16"
        };

        var matrix = new List<List<String>>();
        foreach (var line in list)
        {
            matrix.Add(line.Split('.').ToList());
        }
        StringBuilder html = new StringBuilder();
        WriteLevel(html, matrix, 0);
        Console.WriteLine(html.ToString());
    }

    static void WriteLevel(StringBuilder html, List<List<String>> matrix, int level)
    {
        var nodes = from node in matrix
                    where node.Count > level
                    group node by node[level] into grouping
                    select grouping;
        if (nodes.Count() > 0)
        {
            html.Append("<ul>");
            foreach (var node in nodes)
            {
                html.Append("<li>");
                html.Append(node.Key);
                WriteLevel(html, node.ToList(), level + 1);
                html.Append("</li>");
            }
            html.Append("</ul>");
        }
    }