On Thu, Nov 29, 2001 at 03:17:39PM +0200, Ariel Scolnicov wrote:
> > Yesterday, I saw an interesting related exercise. Write a program that
> > reads the lines from a file and outputs the middle line. The kicker is
> > that you can't use arrays.
I'll interpret that as O(1) memory, O(n) time.
> #!/usr/local/bin/perl -w
> # Print middle line of file(s)
> use strict;
> open F,$ARGV[0] or die;
> open G,$ARGV[0] or die;
> my $l;
> 1 while (defined(<F>) && defined($l=<G>) && defined(<F>));
> print $l;
That requires reading each line three times. Here's one where each
line only need be read once:
use File::ReadBackwards;
open F, $ARGV[0] or die;
tie *G, 'File::ReadBackwards', $ARGV[0] or die;
while(1) {
$front = <F>;
last if $front eq $back;
$back = <G>;
last if $front eq $back;
}
print $front;
--
Michael G. Schwern <[EMAIL PROTECTED]> http://www.pobox.com/~schwern/
Perl Quality Assurance <[EMAIL PROTECTED]> Kwalitee Is Job One
Monkey tennis
