RogerBW's Blog

I’ve been doing the Perl Weekly Challenges. The latest was about printing in octal and detecting balanced brackets.

Printing the numbers from 0 to 50 in octal is, well, trivial, because we have printf.

foreach (0..50) {
  printf('Decimal %d = Octal %o'."\n",$_,$_);
}

Balancing the brackets is more fun. Generating a random string of brackets is easy enough (I make sure the number of characters is even, because if not it won't be balanced anyway).

my $s='';
foreach (-1..2*(int(rand()*4))) {
  $s .= (rand()<0.5)?'(':')';
}

Then I repeatedly delete all matched sets of () until there are none left.

while ($s =~ s/\(\)//g) {
}

Thus (()))())() becomes ())) becomes )).

If there are any characters left, the string was unbalanced.