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Re: Compare two arrays of simple numbers

by Prof Vince (Friar)
on Oct 03, 2007 at 08:24 UTC ( #642339=note: print w/ replies, xml ) Need Help??


in reply to Compare two arrays of simple numbers

That can be solved in linear time with an auxiliary array.

sub comp { my ($a, $b) = @_; return 0 if @$a != @$b; my @c; ++$c[$_] for @$a; --$c[$_] for @$b; $_ != 0 && return 0 for grep defined, @c; return 1; }


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Re^2: Compare two arrays of simple numbers
by erroneousBollock (Curate) on Oct 03, 2007 at 08:27 UTC
    return 0 if @$a != @$b;
    Well that's (worst case) O(n) right there. :-)

    Does != even have a meaning in list context ?

    Update: Ouch, I'm so wrong it's ridiculous.

    -David

      Well that's (worst case) O(n) right there. :-)
      That's what linear means.
      Does != even have a meaning in list context ?
      Edit: It doesn't force scalar context, but seems to compare array lengths. See :
      sub zero { return (0, 0) } print +(zero() == 2) ? "scalar\n" : "list\n"; my @a = (0, 1); my @b = (1, 0); my @c = (0, 2 , 1); print +(@a == @b) ? "same length\n" : "not\n"; print +(@a == @c) ? "same length\n" : "not\n";
      Anyway, I think perl doesn't actually build the lists and directly optimize that to the array size, which should make it constant time.

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