Demonstrating binary search of an array : Array Sort Reverse « Collections « VB.Net Tutorial

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2. Collections
3. Array Sort Reverse

Public Class Tester
    Dim Shared array1 As Integer() = New Integer(14) {}

    Public Shared Sub Main

      Dim i As Integer

      For i = 0 To array1.GetUpperBound(0)
         array1(i) = 2 * i
      Next

      Dim searchKey As Integer = 8

      Dim element As Integer = BinarySearch(array1, searchKey)

      If element <> -1 Then
         Console.WriteLine("Found value in element " & element)
      Else
         Console.WriteLine("Value not found")
      End If


    End Sub

   ' performs binary search
   Shared Function BinarySearch(ByVal array As Integer(), _
      ByVal key As Integer) As Integer

      Dim low As Integer = 0                 ' low index
      Dim high As Integer = array.GetUpperBound(0) ' high index 
      Dim middle As Integer             ' middle index

      While low <= high
         middle = (low + high) \ 2

         If key = array(middle) Then     ' match
            Return middle
         ElseIf key < array(middle) Then ' search low end
            high = middle - 1            ' of array
         Else
            low = middle + 1
         End If

      End While

      Return -1 ' search key not found
   End Function ' BinarySearch

End Class

Found value in element 4