The NPL puzzle for 6 oct was an interesting little Perl exercise [I'm not
sure how to solve it analytically --- I played with it some to little
avail --- but it was certainly subject to brute force, and it turned out
to be a cute little thing.
Write out the digits from 1-9 in order. Then add some plus (+) signs
and times (x) signs to the string to make it add up to 2,002. As
usual in arithmetic, multiplication is done before addition, and you
don't have to put a sign between every 2 digits. The answer is
unique.
What's odd is that my little Perl program found *TWO* solutions, but one
is potentially ambiguous [in particular, given those rules, what should
the value of "a*b*c" be?-- it doesn't say whether things should be done
left-to-right or right-to-left, so perhaps that could be used to exclude
one of the two solutions.
Anyhow, here's the little program I whipped up for it... the fun part is
that it is one of the rare times that counting base-3 is useful:
for (my $count = 0; $count < 3**8; $count += 1)
{ my $try = fixstr($count) ;
print $try,"\n" if eval($try) == 2002 ;
}
exit ;
sub fixstr
{ my $key = $_[0] ;
my $str = "123456789" ;
for (my $i = 8; $i > 0; $i -= 1)
{ my $next = $key % 3 ;
$key = int($key/3) ;
next unless $next ;
substr ($str, $i, 0, $next == 1? '+': "*") ;
}
return $str ;
}
Obviously I'm not a golfer, but I'm wondering if there are any other
interesting approaches to the problem... [base-3 and eval seemed pretty
clean/cute to me]
/Bernie\
--
Bernie Cosell Fantasy Farm Fibers
mailto:[EMAIL PROTECTED] Pearisburg, VA
--> Too many people, too few sheep <--
