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为什么代码会改变分隔符

tag-icon • tag-icon microsoft-excel vba
为什么代码会改变分隔符

我是 Excel VBA 的新手，正在通过修改/更改现有代码进行学习。我尝试了一些代码，这些代码接受一个字符串并给出下一个排列。我的数据在单元格 A1 中，由逗号分隔的数字组成。它将分隔符视为数据的一部分。如果我尝试排列两位数（10 等），它会将它们视为 1 和 0。

Function nextPerm(s As String)
' inspired by http://stackoverflow.com/questions/352203/generating-permutations-lazily
' this produces the "next" permutation
' it allows one to step through all possible iterations without having to have them
' all in memory at the same time
    Dim L As Integer, ii As Integer, jj As Integer
    Dim c() As Byte, temp As Byte

    L = Len(s)

    If StrComp(s, "**done**") = 0 Or StrComp(s, "") = 0 Then
        nextPerm = ""
        Exit Function
    End If

' convert to byte array... more compact to manipulate
    ReDim c(1 To L)
    For ii = 1 To L
        c(ii) = Asc(Mid(s, ii, 1))
    Next ii

' find the largest "tail":
    For ii = L - 1 To 1 Step -1
        If c(ii) < c(ii + 1) Then Exit For
    Next ii

' if we complete the loop without break, ii will be zero
    If ii = 0 Then
        nextPerm = "**done**"
        Exit Function
    End If

' find the smallest value in the tail that is larger than c(ii)
' take advantage of the fact that tail is sorted in reverse order
    For jj = L To ii + 1 Step -1
        If c(jj) > c(ii) Then
            ' swap elements
            temp = c(jj)
            c(jj) = c(ii)
            c(ii) = temp
            Exit For
        End If
    Next jj

' now reverse the characters from ii+1 to the end:
    nextPerm = ""
    For jj = 1 To ii
        nextPerm = nextPerm & Chr(c(jj))
    Next jj
    For jj = L To ii + 1 Step -1
        nextPerm = nextPerm & Chr(c(jj))
    Next jj
End Function

我需要做哪些改变才能使其工作？

答案1

这是逗号分隔列表的版本：

Function nextPerm2(s As String)
' inspired by http://stackoverflow.com/questions/352203/generating-permutations-lazily
' this produces the "next" permutation
' it allows one to step through all possible iterations without having to have them
' all in memory at the same time
    Dim L As Integer, ii As Integer, jj As Integer
    Dim c() As Variant, temp As Variant

    L = Len(s)

    If StrComp(s, "**done**") = 0 Or StrComp(s, "") = 0 Then
        nextPerm2 = ""
        Exit Function
    End If

' convert to byte array... more compact to manipulate
    arr = Split(s, ",")

    ReDim c(1 To UBound(arr) + 1)
    For ii = 1 To UBound(arr) + 1
        c(ii) = arr(ii - 1)
    Next ii
    L = UBound(arr) + 1
' find the largest "tail":
    For ii = L - 1 To 1 Step -1
        If c(ii) < c(ii + 1) Then Exit For
    Next ii

' if we complete the loop without break, ii will be zero
    If ii = 0 Then
        nextPerm2 = "**done**"
        Exit Function
    End If

' find the smallest value in the tail that is larger than c(ii)
' take advantage of the fact that tail is sorted in reverse order
    For jj = L To ii + 1 Step -1
        If c(jj) > c(ii) Then
            ' swap elements
            temp = c(jj)
            c(jj) = c(ii)
            c(ii) = temp
            Exit For
        End If
    Next jj

' now reverse the characters from ii+1 to the end:
    nextPerm2 = ""
    For jj = 1 To ii
        nextPerm2 = nextPerm2 & c(jj) & ","
    Next jj
    For jj = L To ii + 1 Step -1
        nextPerm2 = nextPerm2 & c(jj) & ","
    Next jj

    If Right(nextPerm2, 1) = "," Then nextPerm2 = Left(nextPerm2, Len(nextPerm2) - 1)
End Function

解析用途Split()并且还有其他变化。

未经过全面测试！

在此处输入图片描述

答案2

我没有改变初始帖子中的算法：

但我确实将 VBA 代码修改为更具描述性的变量名，并允许在初始字符串中使用分隔符作为参数：

Option Explicit

Public Sub ShowPerm()

    With Sheet1
        .Range("B1") = nextPerm2(.Range("A1"))
        .Range("B2") = nextPerm2(.Range("A2"), " ")
        .Range("B3") = nextPerm2(.Range("A3"), " ")
        .Range("B4") = nextPerm2(.Range("A4"))
    End With

    'if A1 = "3,2,5,4,1"    Then B1 = "3,4,1,2,5"
    'if A2 = "3 222 5 4 1"  Then B2 = "3 4 1 222 5"
    'if A3 = "1"            Then B3 = "**done**"
    'if A4 = "2"            Then B4 = "**done**"

End Sub

Public Function nextPerm2(ByVal strIni As String, _
                          Optional ByVal delim As String = ",") As String

'inspired by http://stackoverflow.com/questions/352203/generating-permutations-lazily
'this produces the "next" permutation it allows one to step through all possible
'iterations without having to have them all in memory at the same time

    Dim arr As Variant, arrSz As Long, i As Long, j As Long, tmp As Byte

    If strIni = "**done**" Or Len(strIni) = 0 Then Exit Function

    arr = Split(strIni, delim)      'convert to array

    arrSz = UBound(arr)

    For i = 0 To arrSz
        arr(i) = Trim(arr(i))       'clean-up white-spaces from each item
    Next i
    For i = arrSz - 1 To 0 Step -1  'find the largest "tail"
        If arr(i) < arr(i + 1) Then Exit For
    Next i
    If i = 0 Or i = -1 Then         'if loop complete, i is 0; if i = -1, arrSz = 0
        nextPerm2 = "**done**"
        Exit Function
    End If

    'find the smallest value in the tail that is larger than arr(i)
    'take advantage of the fact that tail is sorted in reverse order
    For j = arrSz To i + 1 Step -1
        If arr(j) > arr(i) Then     'swap elements
            tmp = arr(j)
            arr(j) = arr(i)
            arr(i) = tmp
            Exit For
        End If
    Next j

    'now reverse the characters from i + 1 to the end
    nextPerm2 = vbNullString
    For j = 0 To i
        nextPerm2 = nextPerm2 & arr(j) & delim
    Next j
    For j = arrSz To i + 1 Step -1
        nextPerm2 = nextPerm2 & arr(j) & delim
    Next j

    nextPerm2 = Left(nextPerm2, Len(nextPerm2) - 1) 'remove last delim

End Function

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