how to Find and count duplicate numbers in a string array in vb.net?

Question

how to count the duplicate numbers exist in a string or integer array in vb.net?

Dim a as string = "3,2,3"

from the above "a" variable i want a count of "3" as 2 (i mean 3 exist 2 times) and "2" as "1". So how do i make it in vb.net?????

Actually i will get the above string "a" from the sql database. so i dont know which numbers are there. That's why i am asking here.

Answer 1

You've already got some good answers to choose from, but I thought you'd be interested in a one liner solution.

Module Module1
    Sub Main()
        Dim str() As String = "1,2,1,2,3,1,0,1,4".Split(","c)
        str.Distinct().ToList().ForEach(Sub(digit) Console.WriteLine("{0} exists {1}", digit, str.Count(Function(s) s = digit)))
        Console.ReadLine()
    End Sub
End Module

Explanation as to what's happening:

• str.Distinct() - Returns an IEnumerable object of all unique items in the array
• .ToList() - Turns the IEnumerable object into a List<T>
• .ForEach() - Iterates through the List<T>
  • Sub(digit) - Defines an Action delegate to perform on each element. Each element is named digit during each iteration.
  • You should know what Console.WriteLine() is doing
  • str.Count() - Will count each occurrence a digit that satisfies a condition
    • Function(s) s = digit - Defines a Func delegate that will count each occurrence of digits in the array. Each element, in str(), during the Count iterations are stored in the variable s and if it matches the digit variable from Sub(digit) it will be counted

Results:

1 exists 4
2 exists 2
3 exists 1
0 exists 1
4 exists 1