i love these problems,
YuckFoo. i think i should pick up one of these books you've been reading. i keep my skills sharp with martin gardner's puzzlers (
here's a book list. )
okay, so this code's a little evil :P
i should probably document it a bit.... here goes:
#!/usr/bin/perl
use strict;
use warnings;
$|++;
# is using Algorithm::FastPermute cheating? i hope not.
use Algorithm::FastPermute qw/ permute /;
## use Data::Dumper; # see what's inside...
( @ARGV == 2 and $ARGV[0] < $ARGV[1] ) # process arguments
? my( $lower, $upper ) = @ARGV
: die 'usage: ' . $0 . ' lower upper' . $/;
NUMBER: for my $try ( $lower..$upper )
{ # try each number within bounds
my @digits = split //, '*' . $try; # makes ( '*', 1, 2, 3, etc )
my @permutations; # holds permutations
# push permutations onto array
# unless the permutation has a '*' on either end
permute {
push @permutations, [ @digits ]
unless @digits->[-1] eq '*' or @digits->[0] eq '*';
} @digits;
## # uncomment to see what's inside...
## print Dumper \@permutations;
my %results = # product => operation pairs
map { eval( $_ ) || 0, $_ } # create pair
map { join( '', @{ $_ } ) } # stringify the array
@permutations; # for each permutation
## # uncomment to see what's inside...
## print Dumper \@permutations;
defined $results{ $try } # if i found one
&& print( $try, # print it
' is vampire (',
$results{ $try }, # and how i got there
')', $/ )
&& next NUMBER;
}
~Particle *accelerates*
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