Miha Radej wrote:
I don't get why they'd start a sequence halfway through the
alphabet... I assume that there is never more than 23 parts to the
file (22 alpha's + the base).
They have a script which scans the files periodically and usually just
leaves the last few versions of their projects on the disks.
Ah, ok, sound like OpenVMS file versioning. Yes, I can sympathise. When
you're finished with the big stick, may I borrow it?
If it's any consolation we have a file versioning system that starts
with FILENAME.EXT and goes to FILENAM1.EXT .. FILENAM9.EXT and then
moves left a character with FILENA10.EXT .. FILENA99.EXT. If you already
have a FILENAM9.EXT that get's overwritten!
First I take a look at the versions and if both versions "a" and "z"
exist in an array of files. If so, I use this sort:
@newlist = sort round_robin_sort @filelist;
# use only if both a and z versions are found
sub round_robin_sort
{
# drop extension
@alist = split (/\./, $a);
@blist = split (/\./, $b);
# drop the extension
pop @alist;
pop @blist;
$aver = chop ($alist[$#alist]);
$bver = chop ($blist[$#blist]);
# if versions are from different halves of the alphabet
elsif (($aver =~ /[a-k]/) && ($bver =~ /[l-z]/)) { return 1; }
elsif (($bver =~ /[a-k]/) && ($aver =~ /[l-z]/)) { return -1; }
# if both are from first or last half of the alphabet, just cmp
else { return $aver cmp $bver; }
}
shortening it up a bit and making it run like a CASE statement:
sub round_robin_sort{
#assign value of math without extra step
#then return if pattern match fails
return -1 unless($aver)=($a =~/([a-z])\./);
return 1 unless($bver)=($b =~/([a=z])\./);
return 1 if ($aver =~ /[a-k]/) && ($bver =~ /[l-z]/);
return -1 if ($bver =~ /[a-k]/) && ($aver =~ /[l-z]/);
return $aver cmp $bver;
}
OK, so with file system maintenance, you never have so many versions
that they span from z..m. That makes sense. And I suppose you don't have
the gap problem with a shorter list and your two halves solution.
BTW, thanks for the problem, I'm keeping a stack of really odd problems
like this to use when we interview programmers for projects. It's good
to see how they approach problems that are more unusual than they get in
text books.
Steve
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