Introduction
Hello, and welcome to my article. Today, I want to talk about how easy it is to create a Sudoku game with Visual Basic.
What Is Sudoku?
Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9X9 grid with digits so that each column, each row, and each of the nine 3X3 sub-grids that compose the grid contain all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which for a well-posed puzzle has a unique solution. For more information about Sudoku, read this article.
Our Project
I have taken the very long and tedious route to create this project. This means that you have a lot of work to do today, especially on the Design part. Let’s jump straight in, shall we?
Design
Start a new Visual Basic Windows Forms project and design your form to look like Figure 1:
Figure 1: Design
By the looks of the design, you can see that we will be busy today!
Code
Add the following objects that you will use during the course of your program:
Private blnSolution As Boolean = False
Private arrGrid(81) As Integer
Private arrTemp(81) As String
Private arrSolution(81) As String
Private arrButtons(81) As Button
Private rndNumber As New _
System.Random(CType(Now.Ticks _
Mod Int32.MaxValue, Integer))
I created a Boolean (on/off) flag that will determine whether or not a solution has been found. I then created four arrays identifying each button’s text as well as the grid blocks, as you will see later. The last object holds a random number value that we will use to populate the buttons’ text properties on the grid.
Add the Form_Load event:
Private Sub SudokuForm_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
Dim i, j, k As Integer
Dim row, col As Integer
arrButtons(1) = Button1
arrButtons(2) = Button2
arrButtons(3) = Button3
arrButtons(4) = Button4
arrButtons(5) = Button5
arrButtons(6) = Button6
arrButtons(7) = Button7
arrButtons(8) = Button8
arrButtons(9) = Button9
arrButtons(10) = Button10
arrButtons(11) = Button11
arrButtons(12) = Button12
arrButtons(13) = Button13
arrButtons(14) = Button14
arrButtons(15) = Button15
arrButtons(16) = Button16
arrButtons(17) = Button17
arrButtons(18) = Button18
arrButtons(19) = Button19
arrButtons(20) = Button20
arrButtons(21) = Button21
arrButtons(22) = Button22
arrButtons(23) = Button23
arrButtons(24) = Button24
arrButtons(25) = Button25
arrButtons(26) = Button26
arrButtons(27) = Button27
arrButtons(28) = Button28
arrButtons(29) = Button29
arrButtons(30) = Button30
arrButtons(31) = Button31
arrButtons(32) = Button32
arrButtons(33) = Button33
arrButtons(34) = Button34
arrButtons(35) = Button35
arrButtons(36) = Button36
arrButtons(37) = Button37
arrButtons(38) = Button38
arrButtons(39) = Button39
arrButtons(40) = Button40
arrButtons(41) = Button41
arrButtons(42) = Button42
arrButtons(43) = Button43
arrButtons(44) = Button44
arrButtons(45) = Button45
arrButtons(46) = Button46
arrButtons(47) = Button47
arrButtons(48) = Button48
arrButtons(49) = Button49
arrButtons(50) = Button50
arrButtons(51) = Button51
arrButtons(52) = Button52
arrButtons(53) = Button53
arrButtons(54) = Button54
arrButtons(55) = Button55
arrButtons(56) = Button56
arrButtons(57) = Button57
arrButtons(58) = Button58
arrButtons(59) = Button59
arrButtons(60) = Button60
arrButtons(61) = Button61
arrButtons(62) = Button62
arrButtons(63) = Button63
arrButtons(64) = Button64
arrButtons(65) = Button65
arrButtons(66) = Button66
arrButtons(67) = Button67
arrButtons(68) = Button68
arrButtons(69) = Button69
arrButtons(70) = Button70
arrButtons(71) = Button71
arrButtons(72) = Button72
arrButtons(73) = Button73
arrButtons(74) = Button74
arrButtons(75) = Button75
arrButtons(76) = Button76
arrButtons(77) = Button77
arrButtons(78) = Button78
arrButtons(79) = Button79
arrButtons(80) = Button80
arrButtons(81) = Button81
For i = 1 To 81
arrButtons(i).Enabled = False
Next i
End Sub
This is quite straightforward and may seem to be a bit of an overkill. There is method in my madness, however. I didn’t create an array of buttons and calculate each button’s location independently. So, the button array we created holds each button’s (that we created) properties.
Add the next code under the ‘New Game’ button:
Private Sub btnNewGame_Click(ByVal sender _
As System.Object, _
ByVal e As System.EventArgs) _
Handles btnNewGame.Click
CreateGrid()
btnShowSolution.Enabled = True
End Sub
A sub procedure named CreateGrid gets called and the ‘Show Solution’ button becomes enabled. Let’s create the CreatGrid sub procedure now:
Private Sub CreateGrid()
Dim i, j, k As Integer
Dim intRandom As Integer
Dim brnButton As Button
Dim ValIsOK(9) As Boolean
Dim valsOK As Integer = 0
Cursor.Current = Cursors.WaitCursor
For i = 1 To 81
brnButton = arrButtons(i)
brnButton.Text = ""
brnButton.BackColor = _
System.Drawing.Color.LightGray
brnButton.Visible = False
arrSolution(i) = ""
Next i
For i = 1 To 81
If True Then
brnButton = arrButtons(i)
valsOK = GetValidValues(i, ValIsOK)
If valsOK <= 0 Then
' Return False
Exit Sub
End If
intRandom = rndNumber.Next(0, valsOK) + 1
k = 0
For j = 1 To 9
If ValIsOK(j) Then
k = k + 1
If k = intRandom Then
Exit For
End If
End If
Next j
brnButton.Text = j.ToString()
brnButton.BackColor = _
System.Drawing.Color.Gray
End If
Next i
For i = 1 To 81
brnButton = arrButtons(i)
arrSolution(i) = brnButton.Text
intRandom = rndNumber.Next(0, 6 + 1) + 1
If intRandom > 1 Then
brnButton.Text = ""
brnButton.BackColor = _
System.Drawing.Color.LightGray
brnButton.Enabled = True
Else
brnButton.Enabled = False
End If
brnButton.Visible = True
Next i
Cursor.Current = Cursors.Default
End Sub
Add the GetValidValues function that checks to see if the current number is a mathematically valid number to be put in the grid:
Private Function GetValidValues(ByVal Location As Integer, _
ByRef ValidVals As Boolean()) As Integer
Dim i, j, k As Integer
Dim row, col As Integer
Dim strNumber As String
Dim blnValidNumber As Boolean
Dim intReturn As Integer = 0
For i = 1 To 9
blnValidNumber = True
strNumber = i.ToString()
For j = 1 To 9
k = (Int((Location - 1) / 9) * 9) + j
If arrButtons(k).Text = strNumber Then
blnValidNumber = False
Exit For
End If
Next j
If blnValidNumber Then
For j = 1 To 9
k = (((Location - 1) Mod 9) + 1) + _
((j - 1) * 9)
If arrButtons(k).Text = strNumber Then
blnValidNumber = False
Exit For
End If
Next j
End If
If blnValidNumber Then
row = Int(Int((Location - 1) / 9) / 3)
col = Int(((Location - 1) Mod 9) / 3)
For j = 1 To 9
k = (((row * 3) + Int((j - 1) / 3)) * 9) + _
(col * 3) + ((j - 1) Mod 3) + 1
If arrButtons(k).Text = strNumber Then
blnValidNumber = False
Exit For
End If
Next j
End If
ValidVals(i) = blnValidNumber
If blnValidNumber Then
intReturn = intReturn + 1
End If
Next i
Return intReturn
End Function
Add the remaining events:
Private Sub btnExit_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnExit.Click
Close()
End Sub
Private Sub SudokuButton_Click(ByVal sender _
As System.Object, ByVal e As System.EventArgs) _
Handles Button1.Click, Button2.Click, Button3.Click, _
Button4.Click, Button5.Click, Button6.Click, _
Button7.Click, Button8.Click, Button9.Click, _
Button10.Click, Button11.Click, Button12.Click, _
Button13.Click, Button14.Click, Button15.Click, _
Button16.Click, Button17.Click, Button18.Click, _
Button19.Click, Button20.Click, Button21.Click, _
Button22.Click, Button23.Click, Button24.Click, _
Button25.Click, Button26.Click, Button27.Click, _
Button28.Click, Button29.Click, Button30.Click, _
Button31.Click, Button32.Click, Button33.Click,_
Button34.Click, Button35.Click, Button36.Click, _
Button37.Click, Button38.Click, Button39.Click, _
Button40.Click, Button41.Click, Button42.Click, _
Button43.Click, Button44.Click, Button45.Click, _
Button46.Click, Button47.Click, Button48.Click, _
Button49.Click, Button50.Click, Button51.Click, _
Button52.Click, Button53.Click, Button54.Click, _
Button55.Click, Button56.Click, Button57.Click, _
Button58.Click, Button59.Click, Button60.Click, _
Button61.Click, Button62.Click, Button63.Click, _
Button64.Click, Button65.Click, Button66.Click, _
Button67.Click, Button68.Click, Button69.Click, _
Button70.Click, Button71.Click, Button72.Click, _
Button73.Click, Button74.Click, Button75.Click, _
Button76.Click, Button77.Click, Button78.Click, _
Button79.Click, Button80.Click, Button81.Click
Dim i As Integer
Dim blnFound As Boolean = True
Dim btnButton As Button = CType(sender, Button)
If btnButton.Text = "" Then
btnButton.Text = "1"
ElseIf btnButton.Text = "9" Then
btnButton.Text = ""
Else
btnButton.Text = Trim(Str(CInt(btnButton.Text) + 1))
End If
For i = 1 To 81
If arrButtons(i).Text <> arrSolution(i) Then
blnFound = False
Exit For
End If
Next i
End Sub
Private Sub btnShowSolution_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnShowSolution.Click
Dim i As Integer
If blnSolution Then
For i = 1 To 81
arrButtons(i).Text = arrTemp(i)
Next i
btnShowSolution.Text = "Show Solution"
Else
For i = 1 To 81
arrTemp(i) = arrButtons(i).Text
arrButtons(i).Text = arrSolution(i)
Next i
btnShowSolution.Text = "Hide Solution"
End If
blnSolution = Not blnSolution
End Sub
Conclusion
Sudoku is quite a fun game, but being as curious as I am, I just had to see if I could figure out the logic of it. I sincerely hope that you have enjoyed this article. Until next time, cheers!
