Hi, I just noticed that the sequence
1346 1348 1349 1368 1369 1389 1468 1469 1489 1689 3468 3469 3489 3689 4689 has the interesting property of "ascending digits" inside each number. On Tue, Nov 7, 2017 at 7:11 PM, Jimmy Gauvin <[email protected]> wrote: > This problem was solved earlier this year. > > I retained this solution from Arie Groeneveld but there were many others. > It works with numbers and characters. > > vari =: 4 :'y,/@:(],"1 0 -."1)^:(x-1) ,.y' > > 2 vari 'abc' > > ab > > ac > > ba > > bc > > ca > > cb > > > #4 vari 1 3 4 6 8 9 > > 360 > > > > > On Tue, Nov 7, 2017 at 7:07 PM, 'Mike Day' via Programming < > [email protected]> wrote: > >> That number is 360, ie >> (!4) * 4!6 >> as reported on that Quora example’s link. >> >> The comb verbs return the number of combinations, not of permutations. >> >> Cheers, >> >> Mike >> >> >> Please reply to [email protected]. >> Sent from my iPad >> >> > On 7 Nov 2017, at 22:26, 'Skip Cave' via Programming < >> [email protected]> wrote: >> > >> > How many four digit numbers can be formed from the number 1,3,4,6,8 and >> 9 if >> > repetition of digits is not allowed? >> > <https://www.quora.com/How-many-four-digit-numbers-can-be- >> formed-from-the-number-1-3-4-6-8-and-9-if-repetition-of-dig >> its-is-not-allowed> >> > >> > Using Erling's CombE: >> > >> > b =. 4 CombE 6 >> > >> > a =. 1 3 4 6 8 9 >> > >> > #c = b#a >> > >> > 15 NB. so the answer is 15. >> > >> > NB. Convert to decimal >> > >> > 10 10 10 10#. c >> > >> > 1346 1348 1349 1368 1369 1389 1468 1469 1489 1689 3468 3469 3489 3689 >> 4689 >> > >> > >> > Wait a minute! >> > >> > What happened to 1364, 1384, 1396, 1436, 1438, 1439, and lots more? >> > >> > I was hoping CombE would give all combinations of y items taken x at a >> time >> > >> > >> > Skip >> > >> > >> > >> > >> >> >> > ---------------------------------------------------------------------- >> > 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
