*tphyahoo has asked for the wisdom of the Perl Monks concerning the following question:*

Hi, I saw this puzzle mentioned at Does Visual studio Rot the Brain (linked to from slashdot today). The author solved it with c and I thought I'd give it a whack with perl. I didn't google around for solutions, on purpose, cause I wanted to do it myself.
UPDATE: Re the answers I've gotten so far, let me just say, I'm awed. Back to work...

My solution is below. It's been running for a bit, and still hasn't spit out an answer. I'm wondering if anybody out there has a faster way to do it, or if anyone would care to comment on my code.

One thought I had was, I don't really know threads but I wonder... could threads speed this up (obviously at the cost of using more computer resources).

I suspect there are other number theory tricks that could be applied here as well, but I don't know them either.

Well, Over and out monks :)

#What is the largest integer whose digits are all different (and do no +t include 0) that is divisible by each of its individual digits? #Requirements: # -- Integer # -- Digits all different (largest possible would be 987654321) # -- Divisible by each of individual digits # note: # this integer cannot contain the digit 5 if it also contains any e +ven digit, # because then the number would be divisible by 10, and the last di +git would be 0 # similarly, if the last digit is odd, it can't contain any other e +ven digit. use strict; use warnings; my $max_number = 987654321; #my $max_number = 10000; foreach ( 0 .. $max_number - 1 ) { my $test_number = $max_number - $_; print "number / 100000: " . $test_number/100000 . "\n" if $test_nu +mber % 100000 == 0; if ( passes($test_number) ) { print "$test_number passes!\n"; die; } } sub passes { my $test_number = shift() || die "no test number"; my @digits = split("", $test_number); my %seen; my $last_digit; #fail if see the same digit twice. foreach ( @digits ) { return 0 if $_ == 0; #fail if contains 0 return 0 if $seen{$_}; $seen{$_} = 1; } #set the last digit $last_digit = $digits[$#digits]; #fail if contains 5, and any other digit is even #or the last digit is 1, and any other digit is even if ( $seen{5} || $last_digit % 2 == 1 ) { for ( qw(2 4 6 8) ) { return 0 if $seen{$_}; } } for ( keys %seen ) { return 0 unless $test_number % $_ == 0 ; } return 1; }

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