Remove duplicate lists from a parent list using hashset in c#

Question

I have a parent List which contains several child Lists. And these inner Lists contain Column objects.

List<List<Column>> listOfAllColumns;

public class Column
{
    public string SectionName;
    public string StirrupType;
    public int StirrupSize;
    public double StirrupSpacing;
}

Let's say my child Lists contain different Column objects like this:

List1 = {c1, c1, c2}
List2 = {c1, c2, c1}
List3 = {c2, c3}
List4 = {c1,c1, c2}

And the parent List contains these Lists:

listOfAllColumns = {List1, List2, List3, List4}

Now I want a method that removes duplicate lists from the listOfAllColumns list. For example, it will look into the list above and remove list4.

List1: c1,c1,c2
List2: c1,c2,c1
List3: c2,c3
List4: c1,c1,c2 (it is equal to List1 so it is a duplicate)

I know this can be done using Linq and Distinct method but I want to do it using Hashset.

By the way the order is important, so for example {c1, c2, c1} is different than {c2,c1,c1}.

Update 1:

Here is the tricky part. The order is important inside the child lists but it is not important in the parent list. So List1:{c1, c2} and List2: {c2,c1} are different but it is not important how they are added to the Parent List, so listOfAllColumns:{List1, List2} and listOfAllColumns:{List2,Lis1} are the same thing.

Here is the code I have tried:

Column c1 = new Column() { SectionName = "C50", StirrupType = "Tie" };
Column c2 = new Column() { SectionName = "C50", StirrupType = "Spiral" };
Column c3 = new Column() { SectionName = "C40", StirrupType = "Tie" };


List<Column> list1 = new List<Column>() { c1, c1, c2 };
List<Column> list2 = new List<Column>() { c1, c2, c1 };
List<Column> list3 = new List<Column>() { c2, c3 };
List<Column> list4 = new List<Column>() { c1, c1, c2 };


List<List<Column>> listOfAllColumns = new List<List<Column>>() { list1, list2, list3, list4 };


HashSet<List<Column>> hs = new HashSet<List<Column>>();
List<List<Column>> uniquelistOfAllColumns = new List<List<Column>>();

foreach (var c in listOfAllColumns)
{
    if (hs.Add(c))
    {
        // my logic is that hashset should recognize the duplicates in this part.
        uniquelistOfAllColumns.Add(c);
    }
}

A similar question here: C#: Remove duplicate values from dictionary?

Hashset has no order, so if order matters using it, is a nonsense — Blau, Mar 10 '14 at 00:58
@Blau Here is the tricky part. The order is important inside the child lists but it is not important in the parent list. So List1:{c1, c2} and List2: {c2,c1} are different but it is not important how they are added to the Parent List, so listOfAllColumns:{List1, List2} and listOfAllColumns:{List2,Lis1} are the same thing. I updated the question. — Vahid, Mar 10 '14 at 06:30

score 1 · Accepted Answer · answered Mar 10 '14 at 01:35

1

you should override your HashSet methods Contains and Equals (where you can implement the ordered checking).

Then Insert into your implementation of HashSet from you parentList. You will check if the HashSetcontains List<column> and insert if its not there.

But Linq seems to be the best solution.

answered Mar 10 '14 at 01:35

Dexters

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You can reuse [this OrderedSet class](http://stackoverflow.com/a/17853085/122195) – thepirat000 Mar 10 '14 at 01:38
@Dexters I included the code I've been trying to implement. – Vahid Mar 10 '14 at 06:30
1

@Vahid what you are trying to do will work, but you need to implement your own HashSet Contains and Equals routines.. – Dexters Mar 10 '14 at 07:56
@Dexters Thanks. Can you give me a link to an example of implementing these? – Vahid Mar 10 '14 at 08:19
@Dexter Did you look at the link I provided in the question? I wonder why the Hashset method works when we add 'string' types but when we add 'List – Vahid Mar 10 '14 at 08:25

Remove duplicate lists from a parent list using hashset in c#

1 Answers1