Here's one approach:
an0=: 2#0~:_2 +/\ ]
an1=: ({.,(#~ an0)@}.@}:,{:)@(#~ an0)
an2=: an1^:_
an2 1 _1 2 _2{~100?.@#4
2 1 2 1 _2 _1 2 1 1 2 2 2 _1 2 _1 2 1 2 2 2 1 1 _2 _1 2 1 _2 _1 _2 _2
_2 _2 _1 _2 _1 _1 _2 _2 1 1 1 2 1 _2 1 _2 _1 _1 _1 2
#an2 1 _1 2 _2{~100?.@#4
50
I have not convinced myself that there's no ambiguity in this problem,
and my approach seems like it has room for improvement, but I get the
same result you got.
Thanks,
--
Raul
On Fri, Dec 6, 2019 at 7:15 AM R.E. Boss <[email protected]> wrote:
>
> Given an array with zero or more annihilating pairs, i.e., two subsequent
> numbers which add up to zero, the question is to clean up the array by
> deleting all annihilating pairs such that no such pairs are left.
> I do have a solution that is both elegant and efficient (I believe), but I am
> curious about other thoughts.
>
> foo 2 1 1 _1 2 _2 _1
> 2
>
> foo 1 _1 2 _2{~100?.@#4 NB. Notice (?.)
> 2 1 2 1 _2 _1 2 1 1 2 2 2 _1 2 _1 2 1 2 2 2 1 1 _2 _1 2 1 _2 _1 _2 _2 _2 _2
> _1 _2 _1 _1 _2 _2 1 1 1 2 1 _2 1 _2 _1 _1 _1 2
>
>
> R.E. Boss
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