二、 游戏规则的算法实现
二十一点游戏是玩家要取得比庄家更大的点数总和，但点数超过二十一点即为爆牌，并输掉注码。J、Q、K算10点，A可算1点或11点，其余按牌面值计点数。“BlackJack”是由一张A和J、Q、K或10所组成。开始时每人发两张牌，一张明，一张暗，凡点数不足二十一点，可选择博牌。如果首两张牌是对子可选择分牌。
为简化起见，程序中只有两个玩家Dealer和Player，都发明牌，无下注过程，不记录输赢，不支持分牌和加倍等。二十一点游戏中，一张牌只要有四个属性说明：Face牌面大小、Suit牌面花色，Count点数，FaceUp牌面是否向上。因此，这里我们不用Card 类而用Card结构。
Structure card
Public face As Integer
Public suit As Integer
Public count As Integer
Public faceup As Boolean
End Structure |
游戏开始时，我们首先要取一副牌，然后将牌洗好，指定从第几张牌开始发起。洗牌时为取得真正的随机数，用My.Computer.Clock.TickCount作产生随机数的种子。
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Dim Deck() As card
Deck = New card(51) {}
Dim TopCard As Integer
Private Sub GetDeck()
Dim i, j As Integer
For i = 0 To 3
For j = 0 To 12
Deck(j + 13 * i).face = j
Deck(j + 13 * i).suit = i
If j < 10 Then
Deck(j + 13 * i).count = j + 1
Else
Deck(j + 13 * i).count = 10
End If
Deck(j + 13 * i).faceup = False
Next
Next
End Sub
Private Sub Shuffle()
Dim i, j, k As Integer
Dim tc As card
For k = 1 To 500
i = CType(My.Computer.Clock.TickCount * Rnd(), Integer) Mod 52
j = CType(Int(Rnd() * 52), Integer)
tc = Deck(i)
Deck(i) = Deck(j)
Deck(j) = tc
Next
topcard = 0
End Sub |
游戏界面中，我们设置三个命令按钮，两个标签。Button1为“发牌”、Button2为“要牌”、Button3为“停牌”。Label1记录庄家点数，Label2记录玩家点数。游戏过程中，如果一副牌发完，立即重洗一副牌，并弹出消息对话框告知。以下列出三个按钮单击事件代码。其中庄家游戏过程中，为简化起见，未曾使用游戏技巧。
Dim playerCount As Integer = 0
Dim playerAce As Integer = 0
Dim dealerCount As Integer = 0
Dim dealerAce As Integer = 0
Dim ipcard, idcard As Integer
Private Sub delay(ByVal dt As Integer)
Dim t As Integer
t = My.Computer.Clock.TickCount
Do
If My.Computer.Clock.TickCount >= t + dt Then Exit Do
Loop
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Button1.Visible = False
Label1.Text=””
Label2.Text=””
Label1.Refresh()
Label2.Refresh()
MyBase.CreateGraphics.Clear(Color.DarkGreen)
dealerAce = 0
playerAce = 0
dealerCount = 0
playerCount = 0
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
playerCount += Deck(TopCard).count
If Deck(TopCard).face = 0 Then playerCount += 10 : playerAce += 1
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
Label2.Text = playerCount.ToString
Label2.Refresh()
delay(1000)
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
dealerCount += Deck(TopCard).count
If Deck(TopCard).face = 0 Then dealerCount += 10 : dealerAce += 1
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
Label1.Text = dealerCount.ToString
Label1.Refresh()
delay(1000)
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 220, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
playerCount += Deck(TopCard).count
If Deck(TopCard).face = 0 And playerAce = 0 Then playerCount += 10 : playerAce += 1
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
Label2.Text = playerCount.ToString
Label2.Refresh()
delay(1000)
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 220, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
dealerCount += Deck(TopCard).count
If Deck(TopCard).face = 0 And dealerAce = 0 Then dealerCount += 10 : dealerAce += 1
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
Label1.Text = dealerCount.ToString
Label1.Refresh()
delay(1000)
ipcard = 2
idcard = 2
Button2.Visible = True
Button3.Visible = True
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200 + 20 * ipcard, 200, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
playerCount += Deck(TopCard).count
If Deck(TopCard).face = 0 Then playerCount += 10 : playerAce += 1
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
ipcard += 1
Label2.Text = playerCount.ToString
Label2.Refresh()
If playerCount > 21 Then
If playerAce >= 1 Then
playerCount -= 10
playerAce -= 1
Label2.Text = playerCount.ToString
Label2.Refresh()
Else
MsgBox("Player loss!")
Button1.Visible = True
Button2.Visible = False
Button3.Visible = False
End If
End If
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Button2.Visible = False
Button3.Visible = False
dealerPlay()
End Sub
Private Sub dealerPlay()
Do
If dealerCount < 17 Then
cdtDrawExt(MyBase.CreateGraphics.GetHdc, 200 + 20 * idcard, 10, 75, 100, (Deck(TopCard).face * 4 + Deck(TopCard).suit), 0, 0)
dealerCount += Deck(TopCard).count
If dealerCount > 21 And dealerAce = 1 Then dealerCount -= 10 : dealerAce -= 1
If Deck(TopCard).face = 0 And dealerCount <= 11 Then dealerCount += 10
TopCard += 1
If TopCard >= 52 Then Shuffle() : MsgBox("NEW DECK!")
idcard += 1
Else
Exit Do
End If
Loop
Label1.Text = dealerCount.ToString
Label1.Refresh()
If dealerCount <= 21 Then
If playerCount > dealerCount Then
MsgBox("Player win!")
Else
MsgBox("Dealer win!")
End If
Else
MsgBox("Player win!")
End If
Button1.Visible = True
Button2.Visible = False
Button3.Visible = False
End Sub |
运行结果如下图所示：
三、 实践与提高
上述编程中,我们用了结构描述Card，对Card的Face取值（A，2，…，K）和Suit取值（Club，Diamond，Heart，Spade）用了数值0-12和0-3表示。游戏规则也作了简化，只有两个玩家，也未对玩家属性（如：财富、下注、所持牌、持牌点数等）进行描述。实践表明，较好的方法是用Card、player类，Face和Suit用枚举型数据。这些，我们可以在编程中逐步地添加完善。
随着编程实践的深入，我们的经验也会随之丰富起来。如何写一系列的类去支持各式游戏（包括升级、斗地主等需要用大小王牌的游戏）？如何记录玩家得分？如何支持网络？如何处理网络游戏中玩家离开？如此等等。经一个月、两个月，一年、两年的实践后，你将成为行家里手。
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