Just for fun, let's compare:
==============================
My Machine:
Ubuntu 17.x
J 805
==============================
NB. Mike's solution
timespacex ' 10#.(#~(3=#@~.)"1) >: 9#.inv i. 9^3'
0.00127 153216
NB. Pascal's solution
perm =: i.@! A. i.
combT =: [: ; ([ ; [: i.@>: -~) ((1 {:: [) ,.&.> [: ,&.>/\. >:&.>@:])^:(0 {::
[) (<i.1 0) ,~ (<i.0 0) $~ -~
timespacex '10 #."1 /:~ >: ,/ ({~ perm@#)"1 ] 3 combT 9'
0.00189 1.1616e6
NB. Jon's solution
NB. Note, possibly not fair, since my solution does not give integer results,
but equivalent array representation of each integer
nr=:3&=@:#@:~. *. -.@:(0&e.)
timespacex '(nr"1#])10 10 10#:i.1000'
0.002559 301568
It seems Mike's solution is fast and uses the least amount of memory.
Interestingly, if I integerify my results:
timespacex ' ". (-.&'' '')@:":"1(nr"1#])10 10 10#:i.1000 '
0.001445 522624
The speed is faster than just leaving as arrays, even though it uses more
memory (I tried this multiple times, it's always faster).
--------------------------------------------
On Sat, 8/12/17, 'Pascal Jasmin' via Programming <programm...@jsoftware.com>
wrote:
Subject: Re: [Jprogramming] Quora problem
To: "programm...@jsoftware.com" <programm...@jsoftware.com>
Date: Saturday, August 12, 2017, 8:33 PM
a general approach that uses much
longer code, but permutations of combinations,
perm =: i.@! A. i.
combT =: [: ; ([ ; [: i.@>: -~) ((1 {:: [)
,.&.> [: ,&.>/\. >:&.>@:])^:(0 {::
[) (<i.1 0) ,~ (<i.0 0) $~ -~
# 10 #."1 /:~ >: ,/ ({~ perm@#)"1
] 3 combT 9
504
________________________________
From: 'Mike Day' via Programming <programm...@jsoftware.com>
To: programm...@jsoftware.com
Sent: Saturday, August 12, 2017 7:15 AM
Subject: Re: [Jprogramming] Quora problem
I think Skip wants all permutations, not just
increasing and decreasing
ones,
so here's an alternative:
5({.,(-@[){.])
10#.(#~(3=#@~.)"1) >: 9#.inv i. 9^3
123 124 125 126 127 983 984 985 986 987
The initial 5 ( ) is of course
just to limit the output!
Any use?
Mike
On 12/08/2017 10:56, 'Jon
Hough' via Programming wrote:
> Not
particularly efficient or terse but here:
>
> inc=:
-.@:(0&e.)@:~.@:(2&(</\)) NB. increasing
> dec=:
-.@:(0&e.)@:~.@:(2&(</\)) NB. decreasing
> mt=: inc +. dec NB. monotonic
>
> (-:9*8) }.
(mt"1 # ] ) 10 10 10 #: i. 1000 NB. strip off the first
9*4 rows.
>
--------------------------------------------
> On Sat, 8/12/17, Skip Cave <s...@caveconsulting.com>
wrote:
>
> Subject:
[Jprogramming] Quora problem
> To:
"programm...@jsoftware.com"
<programm...@jsoftware.com>
> Date: Saturday, August 12, 2017, 6:16
PM
>
> How can I
use J to generate all the possible
>
3-digit integers that can be
>
constructed using the digits 1-9 (no
>
zeros), with no repeated digits in
>
each integer? The sequence starts with
> 123 (smallest) and goes to 987
> (largest). Here's the first few
> integers in the sequence:
>
> 123 124 125 126
127 128 129 132 134 135
> 136 137 138
139 142 143 145 146 147
> 148 149 152
153 154 156 157 158 159
> 162......
>
> Skip
>
> Skip Cave
> Cave Consulting LLC
>
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