Alternative and more C-ish calculation of the
quantity p :
y=: 10
n=: <:2*y
p=. (2!1+i.n) - (-n){.2*2!i.&.<:y
p
0 1 3 6 10 15 21 28 36 45 55 64 72 79 85 90 94 97 99
(i.y),2+i.-.y
0 1 2 3 4 5 6 7 8 9 10 9 8 7 6 5 4 3 2
+/\(i.y),2+i.-.y
0 1 3 6 10 15 21 28 36 45 55 64 72 79 85 90 94 97 99
p -: +/\(i.y),2+i.-.y
1
----- Original Message -----
From: Roger Hui <[EMAIL PROTECTED]>
Date: Saturday, November 25, 2006 10:43 am
Subject: Re: [Jprogramming] zig-zag order
> zz is Oleg's solution. f can be rendered readily
> in C.
>
> zz=: ($ [: /:@; [: <@|.`</. i.)@,~
>
> f=: 3 : 0
> n=. <:2*y
> p=. (2!1+i.n) - (-n){.2*2!i.&.<:y NB. <.//.zz y
> q=. }.<:p,>:{:p NB. >.//.zz y
> z=. (y,y)$0
> for_i. i.y do.
> for_j. i.y do.
> k=. i+j
> c=. 0>.k-y-1
> if. 2|k do. z=. z (<i,j)}~ (k{p)+i-c
> else. z=. z (<i,j)}~ (k{q)-i-c end.
> end.
> end.
> )
>
> f 5
> 0 1 5 6 14
> 2 4 7 13 15
> 3 8 12 16 21
> 9 11 17 20 22
> 10 18 19 23 24
>
> (f -: zz)"0 i.20
> 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
>
>
>
> ----- Original Message -----
> From: bill lam <[EMAIL PROTECTED]>
> Date: Saturday, November 25, 2006 9:00 am
> Subject: Re: [Jprogramming] zig-zag order
>
> > bill lam wrote:
> > > Thanks to everyone for input. I can see how to use /. and /: now.
> > >
> > > btw
> > >
> > sorry hitting the send button accidentally.
> >
> > btw anyone knows how to do it in C or have a pointer? May be
> this
> > serves as an
> > example of "C for J Programmers" :-)
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