Since we know the field is not larger than 1000 1000 :
boxen =: [: #@:~. (i. 1000 1000) ([: ;@:] <@:,;.0)~ [: ([ ,:
-~)/"(2) 2 2 $ "1 ]
A =: _4 ]\ 1 2 4 4 2 3 5 7 3 1 6 5 7 3 8 6
boxen A
26
It won't scale well, but it's a correct and comprehensive answer to the
question as asked, and I produced in less than half a minute. There's value in
that. Screw benchmarks.
BTW, there's a bug in J:
f =: ([: ; <@:,;.0~)
g =: ([: ; <@:,;.0 )~ NB. Should be equivalent
(i. 5 5) f 1 ,: 2
5 6 7 8 9 10 11 12 13 14
(i. 5 5) g 1 ,: 2
|domain error: g
| (i.5 5) g 1,:2
h =: ([: ;@:] <@:,;.0 )~ NB. Workaround
(i. 5 5) h 1 ,: 2
5 6 7 8 9 10 11 12 13 14
-Dan
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