You could simplify the sort slightly and I would recommend adding a
bit more whitespace to delimit the verbs more clearly.
up1 =: dyad define
NB. LIMIT K up DATA
({.x) > +/ ({:x) {. /:~ y
)
On Wed, Jan 5, 2011 at 7:26 AM, Alan K. Stebbens <[email protected]> wrote:
> There is programming puzzle on Programming Praxis for which I volunteered a
> simple J solution, as part of my New Year's resolution to renew interest in
> and help evangelize J.
>
> http://programmingpraxis.com/2010/12/07/ullmans-puzzle/
>
>> This puzzle is due to Jeffrey Ullman:
>>
>> Given a list of n real numbers, a real number t, and an integer k, determine
>> if there exists a k-element subset of the original list of n real numbers
>> that is less than t.
>>
>> For instance, given the list of 25 real numbers 18.1, 55.1, 91.2, 74.6,
>> 73.0, 85.9, 73.9, 81.4, 87.1, 49.3, 88.8, 5.7, 26.3, 7.1, 58.2, 31.7, 5.8,
>> 76.9, 16.5, 8.1, 48.3, 6.8, 92.4, 83.0, 19.6, t = 98.2 and k = 3, the
>> 3-element subset 31.7, 16.5 and 19.6 sums to 67.8, which is less than 98.2,
>> so the result is true.
>>
>> This is a puzzle, so you’re not allowed to look at the suggested solution
>> until you have your own solution.
>>
>> Your task is to write a function that makes that determination.
>
>
> My contribution is at
> http://programmingpraxis.com/2010/12/07/ullmans-puzzle/#comment-2267
>
>> up =: dyad def 0
>> NB. LIMIT K up DATA
>> ({.x)>+/({:x){.(/:{])y
>> )
>
> The tacit expression is not very pretty, and so I didn't even go there for
> this audience.
>
> --
> Alan
>
> ----------------------------------------------------------------------
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>
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