Computer Programming Concepts and Visual Basic David I. Schneider

172 Computer Programming Concepts and Visual Basic
Ordered arrays can be searched more efficiently than unordered arrays. In this section
we use their order to shorten the search. The technique used here is applied to searching
sequential files in Section 7.
EXAMPLE 1
The following program places an ordered list of names into an array, requests a name as input, and
informs the user if the name is in the list. Because the list is ordered, the search of the array ends when
an element is reached whose value is greater than or equal to the input name. On average, only half the
ordered array will be searched. Figure 6-5 shows the flowchart for this search.
‘Create array to hold 10 strings
Dim nom(1 To 10) As String
Private Sub cmdSearch_Click()
Dim n As Integer, name2Find As String
‘Search for a name in an ordered list
name2Find = UCase(Trim(txtName.Text))
n = 0 ‘n is the subscript of the array
Do
n = n + 1
Loop Until (nom(n) >= name2Find) Or (n = 10)
‘Interpret result of search
picResult.Cls
If nom(n) = name2Find Then
picResult.Print “Found.”
Else
picResult.Print “Not found.”
End If
End Sub
Private Sub Form_Load()
‘Place the names into the array
‘All names must be in uppercase
nom(1) = “AL”
nom(2) = “BOB”
nom(3) = “CARL”
nom(4) = “DON”
nom(5) = “ERIC”
nom(6) = “FRED”
nom(7) = “GREG”
nom(8) = “HERB”
nom(9) = “IRA”
nom(10) = “JUDY”
End Sub
[Run, type Don into the text box, and click the command button.]