Represent a self reference table in a text tree

问题

I want to represent a self referencing table in a text tree (like TreeView but in text). I have been working on it and I did good so far. The problem is when I go few levels deep in the tree. So far The result is this:

┌──Main Group 1
│  ├──SubGroup 1.1
│  │  ├──SubGroup 1.1.1
│  │  ├──SubGroup 1.1.2
│  │  ├──SubGroup 1.1.3
│  │  └──SubGroup 1.1.4
│  │     ├──SubGroup 1.1.4.1
│  │     └──SubGroup 1.1.4.2
│  │  │     ├──Problem group 1
│  │  │     ├──Problem group 2
│  │  │     └──Problem group 3
│  │  │  │     └──Problem group 3.1
│  ├──SubGroup 1.2
│  └──SubGroup 1.3
│     ├──SubGroup 1.3.1
│     └──SubGroup 1.3.2
└──Main Group 2
   ├──SubGroup 2.1
   └──SubGroup 2.2

As you can see in the Problem Groups above, the format starts to break and extra lines are showing.

The code I wrote is:

public class Group
    {
        public int ID { get; set; }
        public int? ParentID { get; set; }
        public string Name { get; set; }
    }

    static void Main(string[] args)
    {
        List<Group> groups = new List<Group>();
        groups.Add(new Group { ID = 1, ParentID = null, Name = "Main Group 1" });
        groups.Add(new Group { ID = 2, ParentID = 1, Name = "SubGroup 1.1" });
        groups.Add(new Group { ID = 3, ParentID = 1, Name = "SubGroup 1.2" });
        groups.Add(new Group { ID = 4, ParentID = 1, Name = "SubGroup 1.3" });
        groups.Add(new Group { ID = 5, ParentID = null, Name = "Main Group 2" });
        groups.Add(new Group { ID = 6, ParentID = 5, Name = "SubGroup 2.1" });
        groups.Add(new Group { ID = 7, ParentID = 5, Name = "SubGroup 2.2" });
        groups.Add(new Group { ID = 8, ParentID = 2, Name = "SubGroup 1.1.1" });
        groups.Add(new Group { ID = 9, ParentID = 2, Name = "SubGroup 1.1.2" });
        groups.Add(new Group { ID = 10, ParentID = 2, Name = "SubGroup 1.1.3" });
        groups.Add(new Group { ID = 11, ParentID = 2, Name = "SubGroup 1.1.4" });
        groups.Add(new Group { ID = 12, ParentID = 11, Name = "SubGroup 1.1.4.1" });
        groups.Add(new Group { ID = 13, ParentID = 11, Name = "SubGroup 1.1.4.2" });
        groups.Add(new Group { ID = 14, ParentID = 13, Name = "Problem group 1" });
        groups.Add(new Group { ID = 15, ParentID = 13, Name = "Problem group 2" });
        groups.Add(new Group { ID = 16, ParentID = 13, Name = "Problem group 3" });
        groups.Add(new Group { ID = 17, ParentID = 16, Name = "Problem group 3.1" });
        groups.Add(new Group { ID = 18, ParentID = 4, Name = "SubGroup 1.3.1" });
        groups.Add(new Group { ID = 19, ParentID = 4, Name = "SubGroup 1.3.2" });

        PrintGroupsTree(groups);
        Console.Read();
    }


    static void PrintGroupsTree(List<Group> groups)
    {
        if (groups == null)
            return;

        var rootGroups = groups.Where(grp => grp.ParentID == null);

        foreach (var g in rootGroups)
            PrintRow(0, g, groups);
    }

    private static void PrintRow(int p, Group grp, List<Group> groups)
    {
        string leader = string.Empty;
        string leaderEnd = string.Empty;

        // get the root items
        var rootItems = groups.Where(g => g.ParentID == null);

        // find the leading character
        if (grp == rootItems.First())
        {
            if (rootItems.Count() == 1)
                leader = "─";
            else
                leader = "┌";
        }
        else if (grp == rootItems.Last())
        {
            leader = "└";
        }
        else
        {
            if (p == 0)
                leader = "├";
            else
                if (rootItems.Count() == 1)
                    leader += " ";
                else
                    leader = "│";
        }

        if (grp.ParentID == rootItems.Last().ID)
            leader = " ";

        // if this is a child node
        if (!rootItems.Contains(grp))
        {
            // get the siblings of the current node (same parentID)
            var itemSiblings = groups.Where(g => g.ParentID == grp.ParentID);
            if (grp == itemSiblings.Last())
                leaderEnd = " └";
            else
                leaderEnd = " ├";
        }

        // get the siblings of the parent item (same as parentItem.ParentID)
        var parentItem = groups.Where(g => g.ID == grp.ParentID).SingleOrDefault();
        var parentItemSiblings = groups.Where(g => g.ParentID == parentItem.ParentID);
        if (p > 0)
        {
            leader += " ";
            for (int i = 1; i <= p - 1; i++)
            {
                if (!rootItems.Contains(grp)
                    && parentItem == parentItemSiblings.Last()
                    && i == p - 1)
                    leader += "   ";

                else
                    leader += " │ ";
            }
        }

        // write the group
        string row = leader + leaderEnd + "──" + grp.Name;
        Console.WriteLine(row);

        // recursive calling to the childs of this item
        var childGroups = groups.Where(g => g.ParentID == grp.ID);
        foreach (var g in childGroups)
        {
            PrintRow(p + 1, g, groups);
        }
    }

Is there a way to represent this correctly using a better looking code?

回答1:

This is a problem that requires recursion and you are not taking full advantage of it.

    static void Main(string[] args)
    {     
        List<Group> groups = new List<Group>();               
        ...
        PrintTree(groups, "", null);
    }

    static void PrintTree(List<Group> allGroups, string lead, int? id)
    {
        var children = allGroups.Where(g => g.ParentID == id).ToList();

        if (children.Count > 0)
        {
            int n = children.Count-1;

            for (int i = 0; i < n; i++)
            {
                Console.WriteLine(lead + "├──" + children[i].Name);
                PrintTree(allGroups, lead + "│  ", children[i].ID);                    
            }

            Console.WriteLine(lead + "└──" + children[n].Name);
            PrintTree(allGroups, lead + "   ", children[n].ID);                    
        }
    }

I leave fixing the very first element as an exercise.

来源：https://stackoverflow.com/questions/13070206/represent-a-self-reference-table-in-a-text-tree