我需要在 VBA 中实现良好的 map 类。 这是我对整数键的实现
盒子类:
Private key As Long 'Key, only positive digit
Private value As String 'Value, only
'Value getter
Public Function GetValue() As String
GetValue = value
End Function
'Value setter
Public Function setValue(pValue As String)
value = pValue
End Function
'Ket setter
Public Function setKey(pKey As Long)
Key = pKey
End Function
'Key getter
Public Function GetKey() As Long
GetKey = Key
End Function
Private Sub Class_Initialize()
End Sub
Private Sub Class_Terminate()
End Sub
map 类别:
Private boxCollection As Collection
'Init
Private Sub Class_Initialize()
Set boxCollection = New Collection
End Sub
'Destroy
Private Sub Class_Terminate()
Set boxCollection = Nothing
End Sub
'Add element(Box) to collection
Public Function Add(Key As Long, value As String)
If (Key > 0) And (containsKey(Key) Is Nothing) Then
Dim aBox As New Box
With aBox
.setKey (Key)
.setValue (value)
End With
boxCollection.Add aBox
Else
MsgBox ("В словаре уже содержится элемент с ключем " + CStr(Key))
End If
End Function
'Get key by value or -1
Public Function GetKey(value As String) As Long
Dim gkBox As Box
Set gkBox = containsValue(value)
If gkBox Is Nothing Then
GetKey = -1
Else
GetKey = gkBox.GetKey
End If
End Function
'Get value by key or message
Public Function GetValue(Key As Long) As String
Dim gvBox As Box
Set gvBox = containsKey(Key)
If gvBox Is Nothing Then
MsgBox ("Key " + CStr(Key) + " dont exist")
Else
GetValue = gvBox.GetValue
End If
End Function
'Remove element from collection
Public Function Remove(Key As Long)
Dim index As Long
index = getIndex(Key)
If index > 0 Then
boxCollection.Remove (index)
End If
End Function
'Get count of element in collection
Public Function GetCount() As Long
GetCount = boxCollection.Count
End Function
'Get object by key
Private Function containsKey(Key As Long) As Box
If boxCollection.Count > 0 Then
Dim i As Long
For i = 1 To boxCollection.Count
Dim fBox As Box
Set fBox = boxCollection.Item(i)
If fBox.GetKey = Key Then Set containsKey = fBox
Next i
End If
End Function
'Get object by value
Private Function containsValue(value As String) As Box
If boxCollection.Count > 0 Then
Dim i As Long
For i = 1 To boxCollection.Count
Dim fBox As Box
Set fBox = boxCollection.Item(i)
If fBox.GetValue = value Then Set containsValue = fBox
Next i
End If
End Function
'Get element index by key
Private Function getIndex(Key As Long) As Long
getIndex = -1
If boxCollection.Count > 0 Then
For i = 1 To boxCollection.Count
Dim fBox As Box
Set fBox = boxCollection.Item(i)
If fBox.GetKey = Key Then getIndex = i
Next i
End If
End Function
如果我插入 1000 对键值，一切正常。但如果是 50000，程序就会卡住。
我该如何解决这个问题？或者也许还有更好的解决方案？
最佳答案
您的实现的主要问题是操作 containsKey 非常昂贵( O(n) complex )，并且在每次插入时都会调用它，即使它“知道”结果是什么，它也永远不会中断.
这可能会有所帮助:
...
If fBox.GetKey = Key Then
Set containsKey = fBox
Exit Function
End If
...
为了降低 containsKey 复杂性，典型的做法是
- 对键进行排序，以便您可以使用 binary search而不是线性搜索
- 将 key 保存在树中或 hashed buckets 中
最简单的方法是使用Collection的内置(希望经过优化)功能通过键存储/检索项目。
商店:
...
boxCollection.Add Item := aBox, Key := CStr(Key)
...
检索(未测试，基于this answer):
Private Function containsKey(Key As Long) As Box
On Error GoTo err
Set containsKey = boxCollection.Item(CStr(Key))
Exit Function
err:
Set containsKey = Nothing
End Function
另请参阅:
关于VBA map 实现，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/27669805/