lr'lr'
5!:5@<
Eesuk's explicit generalization of a classic solution:
lr'involute0'
3 : 0
t=.<./'M N'=.y
p=.,t{.|:(>:i.-N),:i.-M
d=.(+:t)$(,-)1,N
y$/:+/\p#d
)
Eesuk's tacit version:
lr'involute1'
$ /:@(+/\)@(,@(<./ {. |:@(1 0 + [EMAIL PROTECTED]@|.)) # +:@<./ $ (, -)@(1 ,
{:))
A slight variation:
lr'involute2'
([ $ /:@(+/\@(,@(] {. |:@((1 0 + [EMAIL PROTECTED]@|.)@[)) # +:@] $ (, -)@(1 ,
{:@[)))) {.
lr'st'
7!:2 , 6!:2
st'involute0 400 600'
6302784 0.025494581
st'involute1 400 600'
4195328 0.0252504159
st'involute2 400 600'
3155008 0.0255353683
bill lam
Wed Nov 29 11:44:59 HKT 2006
[Jprogramming] spiral order
Did anyone compare timing of vairous solutions presented in this forum with
classic solutions in http://www.jsoftware.com/papers/play132.htm ? It may need
to modify evolute to involute before testing.
Eugene McDonnell wrote:
>
> On Nov 26, 2006, at 12:18 AM, Roger Hui wrote:
>
>> Now that we have mastered zigzag order, how about the
>> spiral order? For example, the spiral order for a
>> 4 5 array is:
>>
>> 0 1 2 3 4
>> 13 14 15 16 5
>> 12 19 18 17 6
>> 11 10 9 8 7
>>
>
> My At Play With J article "Volutes" in Vector 13.2 (October 1996) gives
> several solutions to the problem, but I doubt many people could improve
> Joey Tuttle's amazing one.
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
