C#

ArrayList paths = {the file split line by line into an arraylist}

private void Run()
{
    treeView1.Nodes.Add("root");
    Buildtree("root", treeView1.Nodes[0]);
}
    
private void Buildtree(String path, TreeNode parentNode)
{
    ArrayList directories = GetDirectories(path);
    if (directories.Count != 0)
    {
        foreach (string directory in directories)
        {
            TreeNode node = new TreeNode(directory.Remove(0, path.Length + 1));
            parentNode.Nodes.Add(node);

            Buildtree(directory, node);
        }
    }
}

private ArrayList GetDirectories(string parentPath)
{
    ArrayList directories = new ArrayList();
    foreach (string path in paths)
    {
        if (path.StartsWith(parentPath))
        {
            bool hasSubdir = false;

            if (path.Contains('/') && (path.Length > parentPath.Length))
            {
                int startpos = parentPath.Length + 1;
                string leftover = path.Substring(startpos, path.Length - startpos);
                if (!string.IsNullOrEmpty(leftover) && leftover.Contains('/')) hasSubdir = true;
            }

            if (!hasSubdir && (path != parentPath))
                directories.Add(path);
        }
    }
    return directories;
}