class as tree (class that contain list of it's type)

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I have this class StudentsGroup that also contain HashSet<StudentsGroup>

C#

public class StudentsGroup
{
    public string Name;
    public int StudentsCount;
    public HashSet<StudentsGroup> SubGroups;

    public StudentsGroup()
    {
        SubGroups = new HashSet<StudentsGroup>();
        Name = "no_name";
    }
    public StudentsGroup(string name,int studens_count=0):this()
    {
        Name = name;
        StudentsCount = studens_count;
    }
}

how can I add element to SubGroups and its SubGroups in hierarchical way.
for example i can add item using this code

C#

//ex AddGroup(new StudentsGroup("first year, section one,group 1,subgroup 1"),0,0,0);
            this.SubGroups.
                ElementAt(0).SubGroups.
                ElementAt(0).SubGroups.
                ElementAt(0).SubGroups.
                Add(new StudentsGroup("first year , section one , group 1 , subgroup 1"));

Now how can I implement function AddGroup that take element instance and parent index,and if parent not exist return error

C#

public void AddGroup(StudentsGroup group, params int[] ParentIndex)
{
    //method body
}

what I mean
compare these two case

C#

StudentsGroup school = new StudentsGroup("school");
//add three years each year contain two classes
school.SubGroups.Add(
	new StudentsGroup("year1"));
 school.SubGroups.Add(
	new StudentsGroup("year2"));
 school.SubGroups.Add(
	new StudentsGroup("year3"));
school.SubGroups.ElementAt(0).SubGroups.Add(
	new StudentsGroup("class1"));
school.SubGroups.ElementAt(0).SubGroups.Add(
	new StudentsGroup("class2"));
school.SubGroups.ElementAt(1).SubGroups.Add(
	new StudentsGroup("class1"));
school.SubGroups.ElementAt(1).SubGroups.Add(
	new StudentsGroup("class2"));
school.SubGroups.ElementAt(2).SubGroups.Add(
	new StudentsGroup("class1"));
school.SubGroups.ElementAt(2).SubGroups.Add(
	new StudentsGroup("class2"));
//if i implement AddGroup(group,parent index)
school.AddGroup(new StudentsGroup("year1"), 0);
school.AddGroup(new StudentsGroup("year2"), 0);
school.AddGroup(new StudentsGroup("year3"), 0);
school.AddGroup(new StudentsGroup("class1"), 0,0);
school.AddGroup(new StudentsGroup("class2"), 0, 0);
school.AddGroup(new StudentsGroup("class1"), 0, 1);
school.AddGroup(new StudentsGroup("class2"), 0, 1);
school.AddGroup(new StudentsGroup("class1"), 0, 2);
school.AddGroup(new StudentsGroup("class2"), 0, 2);

//and how about when we have 10 level of subGroups , dynamic add using method will facilitate code writing

Posted 15-Apr-13 11:56am

ibrahim_ragab

Updated 15-Apr-13 13:10pm

v3

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Comments

Sergey Alexandrovich Kryukov 15-Apr-13 18:11pm

Looks trivial. So, what's the problem? What did you try? If you try something, why your attempt was unsatisfactory?
—SA

ibrahim_ragab 15-Apr-13 19:04pm

NOT trivial

Sergey Alexandrovich Kryukov 15-Apr-13 19:11pm

Hm. It does not cancel my question, apparently...
—SA

ibrahim_ragab 15-Apr-13 19:22pm

//when we have 10 level subgroups
school.SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.ElementAt(0).SubGroups
.Add(new StudentsGroup("class2"));
//if i implement function AddGroup
school.AddGroup(new StudentsGroup("class2"),0,0,0,0,0,0,0,0,0,0,0);

Sergey Alexandrovich Kryukov 15-Apr-13 20:33pm

OK, and..?
—SA

Steve44 15-Apr-13 23:44pm

Consider re-designing your approach, e.g. using a Dictionary so you can resolve groups by name, etc. Then you can provide a list of names (i.e. the "path within the subgroups") to iteratively resolve the target group you want to identify and then operate on this group as needed. The list would allow you to address any number of levels as required.

ibrahim_ragab 16-Apr-13 12:16pm

Thanks very much Steve44 ,solved

1 solution

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ibrahim_ragab · Accepted Answer · 2013-04-16T06:17:00

Solution 1

C#

public void AddGroup(StudentsGroup group, params int[] ParentIndex)
{
	HashSet<StudentsGroup> last_subGroups = this.SubGroups;
	StudentsGroup current = this;
	for (int i = 1; i < ParentIndex.Length; i++)
	{
		last_subGroups = current.SubGroups;
		current = current.SubGroups.ElementAt(ParentIndex[i]);
	}
	current.SubGroups.Add(group);
}

Posted 16-Apr-13 6:17am

ibrahim_ragab

Updated 16-Apr-13 6:18am

v2

Comments

Steve44 16-Apr-13 13:48pm

Yep, that was the traversal as proposed. However I still think the indexing of a HashSet by ElementAt is resulting in a pretty brittle decision as it can change when adding new sub-groups in the hierarchy.