CODEWITHSUNDEEP
arraysvb.netlinq
AntikM
AntikM

Reputation: 651

Count unique once-occuring elements in an array

I have this problem

Structure Person
    Dim name As String
    Dim age As Integer
End Structure

Dim people(10) As Person

people(0).name = "A"
people(0).age = 21
...
people(9).name = "Z"
people(9).age = 30

Now e.g. if I have the following values for age = {20, 21, 20, 23, 25, 35, 30, 29, 25, 26}

I am trying to identify and eliminate every person from people who has a unique age, i.e., my final people array should only contain records of persons with ages 20,25.

I tried something like this:

tempList() As Int
cleanList() As Int

for i = 0 to people.count - 1
     array.resize(templist, i + 1)
     templist(i) = people(i).age
next

cleanList = tempList.Distinct().ToArray()

The problem is, doing it this way gives me each and every distinct value from the array. But I want only those values which occur only once.

Any help on this?

Thanks a lot!

Upvotes: 0

Views: 341

Answers (3)

Slai
Slai

Reputation: 22876

You can group by .age and get the items from the groups that have more than one item:

Dim cleanList = people.ToLookup(Function(p) p.age).
                       Where(Function(g) g.Count > 1).SelectMany(Function(g) g).ToList

Upvotes: 1

Abdullah Dibas
Abdullah Dibas

Reputation: 1507

Try this:

Dim duplicatePersons = people.Where(Function(p) people.Count(Function(p1) p1.Age = p.Age) > 1).ToArray()

Upvotes: 0

ocuenca
ocuenca

Reputation: 39346

You need to group your list of ages first to get only the repeated values:

Dim ages= From a In allages _
          Group a By Key = a Into Group _
          Where Group.Count() > 1 _
          Select Group.Key

Then you can filter you list of people:

Dim result = From p In people _
             Where ages.Contains(p.age)  _
             Select p

Upvotes: 0

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