TWC249

Challenge Link

Task1

We count the values in a hash, if there are any odd number counts, we return an empty array, else we pair up the elements:

#!/usr/bin/env perl
use strict;
use warnings;
use List::Util qw(all);
use Data::Show;

sub equal_pairs{
  my %h;
  $h{$_}++ foreach @{$_[0]};
  (all{$_%2} values %h) ? () : map{my $k=$_;map{[$k,$k]}1..$h{$k}/2}keys %h;
}

print show equal_pairs([3,2,3,2,2,2]);
print show equal_pairs([1,2,3,4]);

Task2

We initialize two variables $i and $j to 0 and length of the string respectively, if the character in the string is equal to 'I' then we increment $i else we decrement $j, and lastly append the $i to the end of the result:

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Show;

sub di_string_match{
  my ($i,$j) = (0,length $_[0]);
  (map{$_ eq 'I' ? $i++ : $j--}split '',$_[0]),$i;
}

print show di_string_match('IDID');
print show di_string_match('III');
print show di_string_match('DDI');