我在A列中有整数,在B列中,我想显示结果'Prime‘,如果它没有关于数字本身的更多因子。这是这样的,例如,如果数字是37,结果将是'Prime‘,如果数字是44,则结果将是2x2x11。如何使用excel公式完成此操作?屏幕截图:
发布于 2017-03-29 10:50:34
免责声明:下面的代码是从此very useful VB.NET example移植过来的
Option Explicit
Sub Test()
Debug.Print FindFactors(2)
Debug.Print FindFactors(3)
Debug.Print FindFactors(11)
Debug.Print FindFactors(12)
Debug.Print FindFactors(13)
Debug.Print FindFactors(16)
Debug.Print FindFactors(17)
Debug.Print FindFactors(24)
Debug.Print FindFactors(25)
Debug.Print FindFactors(11234)
Debug.Print FindFactors(67894)
End Sub
Function FindFactors(lngNumber As Long) As String
Dim collFactors As Collection
Dim lngFactor As Long
Dim lngCounter As Long
Dim strFactors As String
Dim strFactor As String
Set collFactors = New Collection
' Take out the 2s.
Do While (lngNumber Mod 2 = 0)
collFactors.Add 2
lngNumber = lngNumber / 2
Loop
' Take out other primes.
lngFactor = 3
Do While (lngFactor * lngFactor <= lngNumber)
If (lngNumber Mod lngFactor = 0) Then
' This is a factor.
collFactors.Add lngFactor
lngNumber = lngNumber / lngFactor
Else
' Go to the next odd number.
lngFactor = lngFactor + 2
End If
Loop
' If num is not 1, then whatever is left is prime.
If lngNumber > 1 Then
collFactors.Add lngNumber
End If
' make a string out of collection
strFactors = ""
If collFactors.Count = 1 Then
strFactors = "Prime"
Else
For lngCounter = 1 To collFactors.Count
strFactors = strFactors & collFactors(lngCounter)
If lngCounter < collFactors.Count Then
strFactors = strFactors & "x"
End If
Next lngCounter
End If
FindFactors = strFactors
End Function
输出结果为:
Prime
Prime
Prime
2x2x3
Prime
2x2x2x2
Prime
2x2x2x3
5x5
2x41x137
2x83x409
可以在工作表中使用:
发布于 2017-03-29 07:44:32
下面是一个比较简单的递归版本。它的思想是,一旦你确定了一个因子,你就用这个因子除以这个数字,然后把注意力转移到分解剩下的因子上。
Function Factor(ByVal n As Long, Optional FirstTrial As Long = 2) As String
Dim i As Long
Dim t As Long
Dim limit As Long
Dim rest As String
Dim s As String
If n = 1 Then
Factor = n
Exit Function
End If
limit = Int(Sqr(n))
t = FirstTrial
Do While t <= limit
If n Mod t = 0 Then
rest = Factor(n / t, t)
If rest <> "1" Then
s = t & "x" & rest
End If
Factor = s
Exit Function
Else
If t = 2 Then t = 3 Else t = t + 2
End If
Loop
'if we get here:
Factor = n
End Function
Function PrimeOrFactor(n As Long) As String
Dim s As String
s = Factor(n)
If n = 1 Then
PrimeOrFactor = "Neither"
ElseIf (s) = Trim(n) Then
PrimeOrFactor = "Prime"
Else
PrimeOrFactor = s
End If
End Function
测试结果如下:
Sub test()
Dim i As Long
For i = 1 To 20
Cells(i, 1) = i
Cells(i, 2) = PrimeOrFactor(i)
Next i
End Sub
输出:
发布于 2019-06-05 08:31:51
对上面John Coleman的优秀代码稍作修改,使用下面包含的Mod with Doubles,将允许将整数分解到Excel的15位限制。因子较大的数字可能会明显变慢。例如,在核心i3上,562,951,983,465,953在大约5秒内被正确分解为16,777,259 x 33,554,467。
Function Factor(ByVal n As Double, Optional FirstTrial As Double = 2) As String 'Changed
Dim i As Long
Dim t As Double 'Changed
Dim limit As Long
Dim rest As String
Dim s As String
If n = 1 Then
Factor = n
Exit Function
End If
limit = Int(Sqr(n))
t = FirstTrial
Do While t <= limit
If FMod(t, n) = 0 Then 'Changed
.
.
.
Public Function FMod(a As Double, b As Double) As Double
FMod = a - Fix(a / b) * b
'http://en.wikipedia.org/wiki/Machine_epsilon
'Unfortunately, this function can only be accurate when `a / b` is outside [-2.22E-16,+2.22E-16]
'Without this correction, FMod(.66, .06) = 5.55111512312578E-17 when it should be 0
If FMod >= -2 ^ -52 And FMod <= 2 ^ -52 Then '+/- 2.22E-16
FMod = 0
End If
End Function
https://stackoverflow.com/questions/43081741
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