[Year 12 SofDev] DLTV Exam 1
ATKINSON-BUCK, Damien
Damien.ATKINSON-BUCK at ivanhoe.com.au
Wed Oct 8 22:32:59 EST 2014
Fantastic, thanks Chris that works much better. New VB Code below :)
Module Module1
Dim StudentNo() As Integer = {1, 125, 250, 375, 500, 625, 750, 875, 999}
Sub Main()
Dim low As Integer = 0
Dim high As Integer = 9
Dim result As Boolean = False
Dim searchnum As Integer = 375
Do While low <= high And result = False
Dim middle As Integer = Int((low + high) / 2)
If StudentNo(middle) = searchnum Then
result = True
Dim myMessage As String = "Low " & StudentNo(low) & ", High " & StudentNo(high) & ", Mid " & StudentNo(middle)
MsgBox(myMessage, vbOK, "DONE")
End If
If StudentNo(middle) > searchnum Then
high = middle
Else
low = middle
End If
Loop
End Sub
End Module
Damien Atkinson-Buck
Head of Learning Area: Technology/Arts
[cid:image005.jpg at 01CFE347.CCF9A650]
p: +61 3 9490 3848
e: damien.atkinson-buck at ivanhoe.com.au<mailto:damien.atkinson-buck at ivanhoe.com.au>
f: +61 3 9490 3490
w: www.ivanhoe.com.au<http://www.ivanhoe.com.au/>
w: www.ivanhoe100.com.au<http://www.ivanhoe100.com.au/>
From: Chris Bucknell [mailto:Chris.Bucknell at haileybury.vic.edu.au]
Sent: Wednesday, 8 October 2014 10:00 PM
To: Year 12 Software Development Teachers' Mailing List
Subject: Re: [Year 12 SofDev] DLTV Exam 1
Hi Damien,
I agree with your logic and working (love a bit of VB.NET code). I think that the issue is with the algorithm given (it's wrong with two errors). This algorithm looks like a binary search but instead of returning the quotient (from the sum of the low and high divided by 2) and using this as the middle it looks like it uses the remainder for the middle. Hence why you have your oscillating 1 and 125 (you have assumed zero index arrays for the student datasets - who knows what would happen with non-zero ... probably a blue screen of death). The second error is that the low and high values should hold the index position in the array (not the value in that position).
So if we resolve these the two issues (i.e. 1-use the quotient for generating the middle index value, and 2-use the index of the position of the start and end of the data set in the array) then we'd get something like:
(Note: 0 based array - continue the VB feel :))
Pass
Position
Low
Position
High
Calculation
Quotient
Remainder
Position
Middle
Student(Middle)
Found
1
0
9
(0+9)/2 =
4
1
4
500
False
2
0
4
(0+4)/2=
2
0
2
250
False
3
2
4
(2+4)/2=
3
0
3
375
True
Good catch on this on Damien.
Chris Bucknell
Head of ICT
Chris.Bucknell at haileybury.vic.edu.au<mailto:Chris.Bucknell at haileybury.vic.edu.au>
www.haileybury.vic.edu.au<http://www.haileybury.vic.edu.au>
From: sofdev-bounces at edulists.com.au<mailto:sofdev-bounces at edulists.com.au> [mailto:sofdev-bounces at edulists.com.au] On Behalf Of ATKINSON-BUCK, Damien
Sent: Wednesday, 8 October 2014 5:51 PM
To: Year 12 Software Development Teachers' Mailing List (sofdev at edulists.com.au<mailto:sofdev at edulists.com.au>)
Subject: [Year 12 SofDev] DLTV Exam 1
Hi folks,
I'm just going through the DLTV Exam and can't quite figure the answer to the algorithm question 12 below.
[cid:image006.png at 01CFE347.CCF9A650]
[cid:image007.png at 01CFE347.CCF9A650]
My desk produces,
Pass
Middle
Low
High
Result
StudentNo(Middle)
1
0
1
999
False
1
2
1
0
999
False
125
3
0
1
999
False
1
4
1
0
999
False
125
AND SO ON
I've tried it as vb code below and ended in an infinite loop. Am I missing something blatantly obvious here or can anyone see the fix for this?
Module Module1
Dim StudentNo() As Integer = {1, 125, 250, 375, 500, 625, 750, 875, 999}
Sub Main()
Dim low As Integer = 1
Dim high As Integer = 999
Dim result As Boolean = False
Dim searchnum As Integer = 375
Do While low <= high And result = False
Dim middle As Integer = (low + high) Mod 2
If StudentNo(middle) = searchnum Then
result = True
Dim myMessage As String = "Low " & low & ", High " & high & ", Mid " & middle
MsgBox(myMessage, vbOK, "DONE")
End If
If StudentNo(middle) > searchnum Then
high = middle
Else
low = middle
End If
Loop
End Sub
End Module
Damien Atkinson-Buck
Head of Learning Area: Technology/Arts
p: +61 3 9490 3848
e: damien.atkinson-buck at ivanhoe.com.au<mailto:damien.atkinson-buck at ivanhoe.com.au>
f: +61 3 9490 3490
w: www.ivanhoe.com.au<http://www.ivanhoe.com.au>
w: www.ivanhoe100.com.au<http://www.ivanhoe100.com.au>
[cid:image008.jpg at 01CFE347.CCF9A650]
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