Question

Public Sub BinarySearch_Surname(ByVal BrownieArray() As Brownie_Structure, ByVal SearchItem As String, ByVal LowInt As Integer, ByVal HighInt As Integer)
    Dim ItemFound As Boolean = False
    Dim SearchFailed As Boolean = False
    Dim Midpoint As Integer = Int((LowInt + HighInt) / 2)

    Try
        If BrownieArray(Midpoint).Surname = SearchItem Then
            ItemFound = True
        Else
            If LowInt >= HighInt Then
                SearchFailed = True
            Else
                If BrownieArray(Midpoint).Surname < SearchItem Then
                    **BinarySearch_Surname(BrownieArray, Midpoint + 1, HighInt, ItemFound)
                Else
                    BinarySearch_Surname(BrownieArray, LowInt, Midpoint - 1, HighInt)**
                End If
            End If
        End If
        If SearchFailed = True Then
            MessageBox.Show("Failed to find Suranme in database", "Error Message", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Exit Sub
        End If
        If ItemFound = True Then
            MessageBox.Show("Surname: " & BrownieArray(Midpoint).Surname, "Found", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Exit Sub
        End If
    Catch
        MessageBox.Show("Failed to find , please insert correct infomation and try again", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Exit Sub
    End Try
End Sub

StackOverflow occurs with this recursive algorithm, I know why the error is caused but do not know how to fix it?

Answer 1

This line:

If LowInt >= HighInt Then

Should be:

If LowInt > HighInt Then

This line:

BinarySearch_Surname(BrownieArray, Midpoint + 1, HighInt, ItemFound)

Should be:

BinarySearch_Surname(BrownieArray, SearchItem, Midpoint + 1, HighInt)

This line:

BinarySearch_Surname(BrownieArray, LowInt, Midpoint - 1, HighInt)

Should be:

BinarySearch_Surname(BrownieArray, SearchItem, LowInt, Midpoint - 1)