Combinations Sub: choose(n,k)

[Stellaferox]

Hi,

I developed a sub for computinf the amout of combinations, given a population N, choose subset K (notation: choose(n,k).
Example: how many combinations are possible for 7 cards from 52?
choose(52,7). To compute n!/((n-k)!*k!)
Because this creates an overflow for relatively small numbers I created an alternative and really fast routine.

Sub Choose(nn,kk)
	' effficient Choose method implementation

	If (nn<0) OR (kk<0) Then Msgbox("Invalid negative parameter in Choose()..")
	If (nn<kk) Then Return 0
	If (nn=kk) Then Return 1

	delta = 0
	imax = 0

	If (kk < (nn-kk)) Then 'choose(100,3)
		delta = nn-kk
		imax = kk
	Else 'choose(100,97)
		delta = kk
		imax = nn-kk
	End If

	ans = delta+1
	For i = 2 To imax
		ans = (ans * (delta + i))/i
	Next
	Return ans
End Sub

I am building an application for displaying and storing all possible combinations. When ready I will publish.

Have fun

Marc

[derez]

Marc
Have you seen my answer to your previous thread regarding combinations ?
It might help you...
Combinations function

[Stellaferox]

Hi David,

Yes I have and I find it very useful.
Thank you for that, by the way...
However I needed an application for my main application to find a next combination without using recursive programming.
I found it at:
http://msdn.microsoft.com/msdnmag/is...n/default.aspx
I translated the code a bit and added some for my own code. Now I can use any combination and find its immediate successor or predecessor.
Marc