jbv wrote:
Hi list,
I'm facing a little combination problem in which I'm getting lost...
I have a string tof n letters (n can range from 2 to 20) and I need to produce all possible combinations of n-1 to 2 letters.
for example :
string : ABCD
I'm trying to do it with nested loops but don't get anywhere...
Any idea ?
I'm sure there's a better way - but here's what I came up with ....
The easy way to do it is recursively :
function allsubstrs str put empty into res repeat with i = (the number of chars in str)-1 down to 2 put generate(i,str) after res end repeat return res end allsubstrs
function generate M, str
put the number of chars in str into N
put empty into res
if M = 1 then
repeat for each char c in str
put c & cr after res
end repeat
return res
end if
repeat with i = 1 to N-M+1
put generate(M-1, char i+1 to -1 of str) into temp
repeat for each line L in temp
put char i of str & L & cr after res
end repeat
end repeat
return res
end generate
It can be re-written to use loops instead of recursive calls - but it's more obvious this way.
-- Alex Tweedly http://www.tweedly.net
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