I have made a list called map: map=:362880 9 $ \:~10^i.9 And pan represents all the permutations of 1-9. So what is wrong with this: (#~ 1&p:)+/"1 map*pan ?
___________________________ David Vaughan On 8 Jul 2011, at 14:13, Roger Hui <[email protected]> wrote: > As Dan Bron indicated, if you are looking for pandigital > primes it's best to avoid generating all permutations. > Many of the permutations (e.g. ones where the last digit > is even) are not prime; generating them only to reject them > represents a large wasted effort. > > > > ----- Original Message ----- > From: David Vaughan <[email protected]> > Date: Friday, July 8, 2011 6:03 > Subject: Re: [Jprogramming] Checking permutations > To: Programming forum <[email protected]> > >> Yeah, it is for PE - ive done the other pandigital problems in >> C, but i wanted to try this one in J. >> My biggest problem seems to be trying to flatten the >> pandigitals. E.g. >> >> 9 8 7 6 5 4 3 2 1 >> >> I need to turn into 987654321. Is it possible to do that or do I >> need to do >> 1+2*10+3*100+...+9*100000000? >> >> ___________________________ >> >> David Vaughan >> >> On 8 Jul 2011, at 12:38, Ric Sherlock <[email protected]> wrote: >> >>> 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? > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
