Project Euler? To get the permutations in reverse order you could reverse the string or reverse the list of permutation indicies. i.e. 0 1 2 3 A. 'cba' 3 2 1 0 A. 'abc'
In J you are better off testing the whole array of permutations rather than looping through them, so (1&p: # ]) i. 50 or (#~ 1&p:) i. 50 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 On Fri, Jul 8, 2011 at 10:53 PM, David Vaughan <[email protected]> wrote: > I'm trying to find the highest 1-9 pandigital prime, so I need to get the > permutations in reverse order if possible. Also, how can I apply my primeTest > script to the results? > > primeTest =: 3 : 'if. #@:q:y do. y end. ' > This is what I have so far. The rank of y and of the list of permutations > don't match up, and it feels like my 'if.' approach isnt great. > > Can anyone offer any advice as to how achieve this? > > Thanks. > > ___________________________ > > David Vaughan > > On 8 Jul 2011, at 11:29, Ric Sherlock <[email protected]> wrote: > >> (i.@!@# A. ]) 'abcd' >> or >> (A.~ i.@!@#) 'abcd' >> >> see also: >> http://rosettacode.org/wiki/Find_the_missing_permutation#J >> >> On Fri, Jul 8, 2011 at 9:44 PM, David Vaughan >> <[email protected]> wrote: >>> >>> How would you go about getting all the permutations of a string in J? >>> ___________________________ >>> >>> David Vaughan >>> ---------------------------------------------------------------------- >>> 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
