### Re^2: what is for key pls

by wind (Priest)
 on May 11, 2011 at 02:26 UTC ( #904067=note: print w/replies, xml ) Need Help??

in reply to Re: what is for key pls
in thread what is for key pls

I made a quick and dirty script to see if some combination of + and -'s between all the digits of that string would return 42.

```my \$str = '7c9695cb23a71d851688cc0d7f8b1072';
my @nums = map {hex} split '', \$str;
my @ops = qw(+ -);
my @iter = (0) x (length(\$str) - 1);

MAIN: while (1) {
my @set = (@ops[@iter], '');
my \$newstr = join '', map {\$nums[\$_] . \$set[\$_]} (0..\$#nums);
print "\$newstr\n" if 42 == eval \$newstr;

# Increment
my \$i = \$#iter;
while (++\$iter[\$i] == @ops) {
\$iter[\$i--] = 0;
last MAIN if \$i < 0;
}
}

After running for an hour though, I decided that I needed to test this by hand:

```use List::Util qw(sum);

my \$str = '7c9695cb23a71d851688cc0d7f8b1072';

print sum map {hex} split '', \$str;
=prints
231
=cut

Unfortunately, as you can see, the string contains an odd number of odd digits. This means that no combination of + and -'s between all the digits can return an even number. So there is no simple solution that equals 42

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