Also I. (= >./) expr gives all indices of the maximum, if you ever need that.
-- Raul On Thu, Jun 12, 2014 at 2:39 AM, R.E. Boss <[email protected]> wrote: > (i.>./) gives the (first) index of the maximum. > > > R.E. Boss > > (Add your info to http://www.jsoftware.com/jwiki/Community/Demographics ) > > > > > -----Original Message----- > > From: [email protected] [mailto:programming- > > [email protected]] On Behalf Of Jon Hough > > Sent: donderdag 12 juni 2014 7:37 > > To: [email protected] > > Subject: [Jprogramming] Maximum totient ratio > > > > Another Project Euler... > > > > This time PE #69: http://projecteuler.net/problem=69 > > > > Essentially, find n which has the maximum of n/totient(n), for all > positive > > integers, n, up to 1000000. > > > > At first this seemed easy. I have a verb to calculate the ratio: > > totient=: (- ~:)&.q: > > func =. ] % totient > > then I can find the maximum: > > max=. (>./)"1@:((] % totient)"0) > > > > max 1+i.1000000 > > 5.53939 > > But this gives me the ratio. I need to find n. > > This is a problem, because finding the maximum, the verb, >./ , collapsed > the > > array so I don't think I can use I. or similar verb to get the index > which > gave > > the maximum ratio. So I am not sure how to find the n which gave this > ratio. > > > > A second issue is I think my method seems to not be well thought out > > memory-wise. My method first calculates the ratio for every integer up to > 1 > > million and holds them all in memory. Surely a better way would be to do > > them one at a time and find the maximum as we go. > > In J I am not sure how to do this. I am guessing the recursion verb $: > will need > > to be used. > > Any help appreciated. > > 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
