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用VB实现循环队列算法收藏

發(fā)布時(shí)間：2025/3/20 编程问答 20 豆豆

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??? 在日常代碼編制時(shí)，許多人會(huì)忽略一些最基本的算法，導(dǎo)致代碼冗余，思路不清楚。我曾經(jīng)至少兩次在CSDN里遇到這類問題：我想在頁面的右邊顯示一個(gè)列表，列表長度為20，新加入一個(gè)用戶后，顯示在列表開頭，再加入的用戶，顯示在這個(gè)用戶的下邊，當(dāng)用戶數(shù)量超過20后，擠掉最前面的那一位，第二位加入的用戶成了第一位，依次循環(huán)，保證列表最多顯示20位用戶。當(dāng)然，實(shí)際問題可能與此有些出入，比如Coder是想顯示網(wǎng)友們最近選擇的歌曲列表，但實(shí)際意思差不多。

??? 面對這個(gè)問題，大多數(shù)朋友會(huì)想到使用數(shù)據(jù)。其實(shí)，這完全是一個(gè)隊(duì)列，只不過，這個(gè)隊(duì)列可以循環(huán)使用，在加入隊(duì)列元素時(shí)，如果超過長度，會(huì)自動(dòng)擠掉最先加入的。如果能夠用代碼直接實(shí)現(xiàn)，為什么要用數(shù)據(jù)庫呢？考慮一下，為了提高網(wǎng)站性能，我們絞盡腦汁，卻往往因?yàn)樗悸返钠?#xff0c;導(dǎo)致性能降低。

??? 那么，在VB中如何實(shí)現(xiàn)可循環(huán)的隊(duì)列呢？

??? 為此，我編寫了一個(gè)循環(huán)隊(duì)列類，以滿足上述需要，同時(shí)為了方便在HTML、ASP、WSH的VBScript腳本語言環(huán)境中使用，該類未聲明任何數(shù)據(jù)類型。

??? 首先看一下該循環(huán)隊(duì)列類的源代碼：

'* ************************************************************** *??
'*??? 程序名稱：Queue.cls??
'*??? 程序功能：一個(gè)VB循環(huán)隊(duì)列類??
'*??? 作者：lyserver??
'*??? 聯(lián)系方式：http://blog.csdn.net/lyserver??
'* ************************************************************** *??
'Class Queue '在ASP、WSH、HTML的VBScript腳本中使用時(shí)需加此句??
??? Dim m_Queue() '隊(duì)列??
??? Dim m_RetQueue() '隊(duì)列返回值??
??? Dim m_ReadIndex '列首偏移索引??
??? Dim m_WriteIndex '元素插入偏移索引??
??? Dim m_MaxLen '隊(duì)列最大尺寸??
??????
??? Private Sub Class_Initialize()??
??????? m_ReadIndex = 0??
??????? m_WriteIndex = 0??
??????? m_MaxLen = 20 '隊(duì)列默認(rèn)大小為20??
??????? ReDim m_Queue(m_MaxLen - 1)??
??? End Sub?
??????
??? Private Sub Class_Terminate()??
??????? Erase m_Queue??
??????? Erase m_RetQueue??
??? End Sub?
??????
??? '獲得隊(duì)列大小??
??? Public Property Get MaxLen()??
??????? MaxLen = m_MaxLen??
??? End Property?
??????
??? '設(shè)置隊(duì)列大小??
??? Public Property Let MaxLen(ByVal NewValue)??
??????? If NewValue > 0 Then?
??????????? m_MaxLen = NewValue??
??????????? ReDim m_Queue(m_MaxLen)??
??????? End If?
??? End Property?
??????
??? '插入隊(duì)列元素??
??? Public Sub Insert(ByVal v)??
??????? If m_WriteIndex = m_MaxLen Then '隊(duì)列已滿，擠掉最先插入的元素??
??????????? m_WriteIndex = 0??
??????????? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen??
??????? End If?
??????? m_Queue(m_WriteIndex) = v??
??????? m_WriteIndex = m_WriteIndex + 1??
??? End Sub?
??????
??? '刪除隊(duì)列元素（按隊(duì)列原則，實(shí)際上是刪除最先插入的元素）??
??? Public Sub Delete()??
??????? Dim vTemp??
??????? m_Queue(m_ReadIndex) = vTemp '將此變量置為未初始化??
??????? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen??
??? End Sub?
??????
??? '清空隊(duì)列??
??? Public Sub Clear()??
??????? ReDim m_Queue(m_MaxLen)??
??????? m_WriteIndex = 0??
??????? m_ReadIndex = 0??
??? End Sub?
??????
??? '獲得隊(duì)列數(shù)組??
??? Public Property Get GetQueue()??
??????? Dim i, n??
??????????
??????? n = 0??
??????? ReDim m_RetQueue(m_MaxLen)??
??????? For i = m_ReadIndex To m_MaxLen - 1??
??????????? If IsEmpty(m_Queue(i)) Then Exit For?
??????????? m_RetQueue(n) = m_Queue(i)??
??????????? n = n + 1??
??????? Next?
??????? For i = 0 To m_ReadIndex - 1??
??????????? If IsEmpty(m_Queue(i)) Then Exit For?
??????????? m_RetQueue(n) = m_Queue(i)??
??????????? n = n + 1??
??????? Next?
??????? GetQueue = m_RetQueue??
??? End Property?
'End Class '在ASP、WSH、HTML的VBScript腳本中使用時(shí)需加此句?
'* ************************************************************** *
'*??? 程序名稱：Queue.cls
'*??? 程序功能：一個(gè)VB循環(huán)隊(duì)列類
'*??? 作者：lyserver
'*??? 聯(lián)系方式：http://blog.csdn.net/lyserver
'* ************************************************************** *
'Class Queue '在ASP、WSH、HTML的VBScript腳本中使用時(shí)需加此句
??? Dim m_Queue() '隊(duì)列
??? Dim m_RetQueue() '隊(duì)列返回值
??? Dim m_ReadIndex '列首偏移索引
??? Dim m_WriteIndex '元素插入偏移索引
??? Dim m_MaxLen '隊(duì)列最大尺寸
???
??? Private Sub Class_Initialize()
??????? m_ReadIndex = 0
??????? m_WriteIndex = 0
??????? m_MaxLen = 20 '隊(duì)列默認(rèn)大小為20
??????? ReDim m_Queue(m_MaxLen - 1)
??? End Sub
???
??? Private Sub Class_Terminate()
??????? Erase m_Queue
??????? Erase m_RetQueue
??? End Sub
???
??? '獲得隊(duì)列大小
??? Public Property Get MaxLen()
??????? MaxLen = m_MaxLen
??? End Property
???
??? '設(shè)置隊(duì)列大小
??? Public Property Let MaxLen(ByVal NewValue)
??????? If NewValue > 0 Then
??????????? m_MaxLen = NewValue
??????????? ReDim m_Queue(m_MaxLen)
??????? End If
??? End Property
???
??? '插入隊(duì)列元素
??? Public Sub Insert(ByVal v)
??????? If m_WriteIndex = m_MaxLen Then '隊(duì)列已滿，擠掉最先插入的元素
??????????? m_WriteIndex = 0
??????????? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen
??????? End If
??????? m_Queue(m_WriteIndex) = v
??????? m_WriteIndex = m_WriteIndex + 1
??? End Sub
???
??? '刪除隊(duì)列元素（按隊(duì)列原則，實(shí)際上是刪除最先插入的元素）
??? Public Sub Delete()
??????? Dim vTemp
??????? m_Queue(m_ReadIndex) = vTemp '將此變量置為未初始化
??????? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen
??? End Sub
???
??? '清空隊(duì)列
??? Public Sub Clear()
??????? ReDim m_Queue(m_MaxLen)
??????? m_WriteIndex = 0
??????? m_ReadIndex = 0
??? End Sub
???
??? '獲得隊(duì)列數(shù)組
??? Public Property Get GetQueue()
??????? Dim i, n
???????
??????? n = 0
??????? ReDim m_RetQueue(m_MaxLen)
??????? For i = m_ReadIndex To m_MaxLen - 1
??????????? If IsEmpty(m_Queue(i)) Then Exit For
??????????? m_RetQueue(n) = m_Queue(i)
??????????? n = n + 1
??????? Next
??????? For i = 0 To m_ReadIndex - 1
??????????? If IsEmpty(m_Queue(i)) Then Exit For
??????????? m_RetQueue(n) = m_Queue(i)
??????????? n = n + 1
??????? Next
??????? GetQueue = m_RetQueue
??? End Property
'End Class '在ASP、WSH、HTML的VBScript腳本中使用時(shí)需加此句
?

??? 然后，我們再來看一下在VB中如何使用此類：

Sub main()??
??? Dim objQueue??
??? Dim i, nLen??
??????
??? Set objQueue = New Queue??
??? '將隊(duì)列長度置為5??
??? nLen = 5??
??? objQueue.MaxLen = nLen??
??????
??? '向隊(duì)列插入元素（不超過隊(duì)列長度）??
??? For i = 1 To nLen??
??????? objQueue.Insert i??
??? Next?
??? '顯示結(jié)果??
??? DisplayQueue objQueue??
?
??? '清空隊(duì)列后重新插入元素（超過隊(duì)列長度）??
??? objQueue.Clear??
??? For i = 1 To nLen + 1??
??????? objQueue.Insert i??
??? Next?
??? '顯示結(jié)果??
??? DisplayQueue objQueue??
??????
??? '刪除隊(duì)列元素??
??? objQueue.Delete??
??? '顯示結(jié)果??
??? DisplayQueue objQueue??
End Sub?
?
Private Sub DisplayQueue(qu)??
??? Dim v(), i??
??? v = qu.GetQueue??
??? For i = 0 To qu.MaxLen - 1??
??????? If IsEmpty(v(i)) Then Exit For?
??????? Debug.Print "第" & i + 1 & "個(gè)元素的值：", v(i)??
??? Next?
??? Debug.Print "------顯示完畢------"?
End Sub?
Sub main()
??? Dim objQueue
??? Dim i, nLen
???
??? Set objQueue = New Queue
??? '將隊(duì)列長度置為5
??? nLen = 5
??? objQueue.MaxLen = nLen
???
??? '向隊(duì)列插入元素（不超過隊(duì)列長度）
??? For i = 1 To nLen
??????? objQueue.Insert i
??? Next
??? '顯示結(jié)果
??? DisplayQueue objQueue

??? '清空隊(duì)列后重新插入元素（超過隊(duì)列長度）
??? objQueue.Clear
??? For i = 1 To nLen + 1
??????? objQueue.Insert i
??? Next
??? '顯示結(jié)果
??? DisplayQueue objQueue
???
??? '刪除隊(duì)列元素
??? objQueue.Delete
??? '顯示結(jié)果
??? DisplayQueue objQueue
End Sub

Private Sub DisplayQueue(qu)
??? Dim v(), i
??? v = qu.GetQueue
??? For i = 0 To qu.MaxLen - 1
??????? If IsEmpty(v(i)) Then Exit For
??????? Debug.Print "第" & i + 1 & "個(gè)元素的值：", v(i)
??? Next
??? Debug.Print "------顯示完畢------"
End Sub
?

??? 看過了VB使用方法后，我們再來看一下在HTML的VBScript腳本中如何使用，需要注意的是，要想測試結(jié)果，必須將以下代碼復(fù)制到記事本后另存為擴(kuò)展名為html或htm的文件，然后使用IE打開，對于類代碼，讀者也可以單獨(dú)取出來存為vbs文件，然后html里包含它就可以了。至于ASP，思路與此完全一樣。

<html>?
?
<head>?
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">?
<title>新建網(wǎng)頁 1</title>?
</head>?
?
<body>?
</body>?
</html>?
<mce:script language=vbscript></mce:script>?
<html>

<body>
</body>
</html>
<mce:script language=vbscript><!--
Option Explicit
'* ************************************************************** *
'*??? 程序名稱：Queue.cls
'*??? 程序功能：一個(gè)VB循環(huán)隊(duì)列類
'*??? 作者：lyserver
'*??? 聯(lián)系方式：http://blog.csdn.net/lyserver
'* ************************************************************** *
Class Queue
?Dim m_Queue() '隊(duì)列
?Dim m_RetQueue() '隊(duì)列返回值
?Dim m_ReadIndex '列首偏移索引
?Dim m_WriteIndex '元素插入偏移索引
?Dim m_MaxLen '隊(duì)列最大尺寸
?
?Private Sub Class_Initialize()
???? m_ReadIndex = 0
???? m_WriteIndex = 0
???? m_MaxLen = 20 '隊(duì)列默認(rèn)大小為20
???? ReDim m_Queue(m_MaxLen - 1)
?End Sub
?
?Private Sub Class_Terminate()
???? Erase m_Queue
???? Erase m_RetQueue
?End Sub
?
?'獲得隊(duì)列大小
?Public Property Get MaxLen()
???? MaxLen = m_MaxLen
?End Property
?
?'設(shè)置隊(duì)列大小
?Public Property Let MaxLen(ByVal NewValue)
???? If NewValue > 0 Then
???????? m_MaxLen = NewValue
???????? ReDim m_Queue(m_MaxLen)
???? End If
?End Property
?
?'插入隊(duì)列元素
?Public Sub Insert(ByVal v)
???? If m_WriteIndex = m_MaxLen Then '隊(duì)列已滿，擠掉最先插入的元素
???????? m_WriteIndex = 0
???????? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen
???? End If
???? m_Queue(m_WriteIndex) = v
???? m_WriteIndex = m_WriteIndex + 1
?End Sub
?
?'刪除隊(duì)列元素（按隊(duì)列原則，實(shí)際上是刪除最先插入的元素）
?Public Sub Delete()
???? Dim vTemp
???? m_Queue(m_ReadIndex) = vTemp '將此變量置為未初始化
???? m_ReadIndex = (m_ReadIndex + 1) Mod m_MaxLen
?End Sub
?
?'清空隊(duì)列
?Public Sub Clear()
???? ReDim m_Queue(m_MaxLen)
???? m_WriteIndex = 0
???? m_ReadIndex = 0
?End Sub
?
?'獲得隊(duì)列數(shù)組
?Public Property Get GetQueue()
???? Dim i, n
????
???? n = 0
???? ReDim m_RetQueue(m_MaxLen)
???? For i = m_ReadIndex To m_MaxLen - 1
???????? If IsEmpty(m_Queue(i)) Then Exit For
???????? m_RetQueue(n) = m_Queue(i)
???????? n = n + 1
???? Next
???? For i = 0 To m_ReadIndex - 1
???????? If IsEmpty(m_Queue(i)) Then Exit For
???????? m_RetQueue(n) = m_Queue(i)
???????? n = n + 1
???? Next
???? GetQueue = m_RetQueue
?End Property

End Class

Sub window_onload
??? Dim objQueue
??? Dim i, nLen

??? Set objQueue=New Queue

??? '將隊(duì)列長度置為5
??? nLen = 5
??? objQueue.MaxLen = nLen
???
??? '向隊(duì)列插入元素（不超過隊(duì)列長度）
??? For i = 1 To nLen
??????? objQueue.Insert i
??? Next
??? '顯示結(jié)果
??? DisplayQueue objQueue

Sub DisplayQueue(qu)
??? Dim v,i
??? v = qu.GetQueue
??? For i = 0 To qu.MaxLen - 1
??????? If IsEmpty(v(i)) Then Exit For
??????? document.write "第" & i + 1 & "個(gè)元素的值：" & v(i) & "<br>"
??? Next
??? document.write "------顯示完畢------<br>"
End Sub
// --></mce:script>

??? 怎么樣？如果讀者覺得不滿意，歡迎您留下寶貴的意見！

發(fā)表于 @ 2009年05月04日 00:15:00|評論(0)|舉報(bào)|收藏

本文來自CSDN博客，轉(zhuǎn)載請標(biāo)明出處：http://blog.csdn.net/lyserver/archive/2009/05/04/4146805.aspx

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