balanced_string_split.pl

#!/usr/bin/env perl
use strict;
use warnings;
use feature 'say';
use DDP;

my @strings = qw/RLRRLLRLRL RLLLLRRRLR LLLLRRRR RLRRRLLRLL LRLLLRRLRR/;

for my $s (@strings) {
  pos $s = 0;
  my $count = 0;
  my ($r, $l) = ('', '');
  my ($l_count, $r_count) = (0, 0);
  while (pos $s < length $s) {
    if ($s =~ /\G(R+)/gc) {
      if ($r) {
        $r .= $1;
        ++$r_count;
      } else {
        $r = $1;
      }
      if ($l) {
        if (length $l == length $r) {
          ++$count;
          $r = $l = '';
        }
      }
    }
    elsif ($s =~ /\G(L+)/gc) {
      if ($l) {
        $l .= $1;
        ++$l_count;
      } else {
        $l = $1;
      }

      if ($r) {
        my $l_len = length $l;
        my $r_len = length $r;
        if ($r_len == $l_len) {
          ++$count;
          $r = $l = '';
        } elsif (!$l_count && !$r_count && $r_len < $l_len) {
          pos $s -= $l_len - $r_len;
          ++$count;
          $r = $l = '';
        }
      }
    } else {
      last;
    }
  }
  say sprintf "%s: %d", $s, $count;
}