You can shave another couple characters by "cheating":
{:(#~ (-:|.)&":"0),*/~901+i.99
906609
But justifying the change from >./ to {: is probably not worth the effort.
Then again, the ultimate in terseness is:
906609
906609
--
Raul
On Sun, Jun 8, 2014 at 11:07 AM, Roger Hui <[email protected]>
wrote:
> Slightly shorter if the formatted results are not converted back into
> numbers:
>
> >./ (#~ (-: |.)@("."0@":)"0) , */~ 100+i. 900
> 906609
> >./ (#~ (-: |.)@":"0) , */~ 100+i. 900
> 906609
>
> A different and perhaps less brutish method is to start with 6-digit
> palindromes and see which ones have two 3-digits factors.
>
>
>
>
> On Sun, Jun 8, 2014 at 8:00 AM, Henry Rich <[email protected]> wrote:
>
> > Brute force seems right for this problem. You could write your solution
> > as
> >
> > >./ (#~ (-: |.)@("."0@":)"0) , */~ 100+i. 900
> >
> > Henry Rich
> >
> > On 6/8/2014 10:46 AM, Jon Hough wrote:
> >
> >> I am pretty pleased that I completed Project Euler Q4.
> >> Question:
> >>
> >>
> >> A palindromic number reads the same both ways. The largest palindrome
> >> made from the product of two 2-digit numbers is 9009 = 91 99.
> >>
> >> Find the largest palindrome made from the product of two 3-digit
> numbers.
> >>
> >>
> >> https://projecteuler.net/problem=4
> >>
> >>
> >> My solution:
> >>
> >> base =. "."0 ":
> >>
> >> NB. Tests if y value is palindrome.
> >> is_palindrome =. (# =)@:(=|.)@:base
> >> NB. multiply all 3 digit nums (100 ~ 999)
> >> mult =: (* is_palindrome"0) @ (*/)
> >> NB. Create list of 3 digit nums.
> >> list =. 100+ i.900
> >>
> >> (>./)@:, list mult list
> >> Although I'm glad got the answer, I'm wondering if it could be made
> >> terser, or if there is a much terser way to solve it? I went for a brute
> >> force approach.
> >> For comparison here is a Haskell answer I found:
> >> maximum[a*b|a<-[100..999],b<-[a..999],reverse(show(a*b))==show(a*b)]
> >> Regards.
> >> ----------------------------------------------------------------------
> >> For information about J forums see http://www.jsoftware.com/forums.htm
> >>
> >> ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> >
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
