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Re^4: swap columns in a 2-dim array

by polettix (Vicar)
on Jun 17, 2005 at 12:26 UTC ( #467676=note: print w/ replies, xml ) Need Help??


in reply to Re^3: swap columns in a 2-dim array
in thread swap columns in a 2-dim array

Unless I am reading his code wrong, it is possible that a given column could be swapped twice and end up in it's original position.
OP uses a shuffled array of 12 different indexes, from which s?he takes six pairs. Each pair contains two different indexes; each index falls into one, and only one, pair; in few words, s?he builds a partitions of the original set into six pairs. Then, s?he performs a single swap using the indexes each pair, which means that each location is read and written exactly once.
I realise that by his original reading, swapping the order of a column twice, so that it ends up back in its original position, meets that criteria.
The OP is also claiming that this is not a homework, so I think that your interpretation is the only possible - that is, an interpretation which looks at the final result and not at useless, noisy intermediate steps.

Flavio (perl -e 'print(scalar(reverse("\nti.xittelop\@oivalf")))')

Don't fool yourself.


Comment on Re^4: swap columns in a 2-dim array
Re^5: swap columns in a 2-dim array
by BrowserUk (Pope) on Jun 17, 2005 at 13:08 UTC

    You're right. I read the first paragraph, scanned the code, saw the FYS function and coded my offering. I'll post a correction.


    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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