TWC258

 Challenge Link

Task1

we split the number into its digits and check if it is even:

#!/usr/bin/env perl
use strict;
use warnings;

sub count_even_digits_number{
  scalar grep{(split'',$_)%2==0}@{$_[0]}
}

printf "%d\n",count_even_digits_number([10,1,111,24,1000]);
printf "%d\n",count_even_digits_number([111,1,11111]);
printf "%d\n",count_even_digits_number([2,8,1024,256]);

Task2

We get the popcount of each index and if it is equal to $k, we include the number at that index in the resultant array, else we skip it:

#!/usr/bin/env perl
use strict;
use warnings;
use ntheory qw(hammingweight);
use List::Util qw(sum0);

sub sum_of_values{
  sum0 map{hammingweight$_==$_[1]?$_[0]->[$_]:()}0..$#{$_[0]}
}

printf "%d\n",sum_of_values([2,5,9,11,3],1);
printf "%d\n",sum_of_values([2,5,9,11,3],2);
printf "%d\n",sum_of_values([2,5,9,11,3],0);

TWC256

Challenge Link

Task1

We check each string with the reverse of all others and increment the count if they are equal:

#!/usr/bin/env perl
use strict;
use warnings;

sub maximum_pairs{
  my ($a) = @_;
  my $c = 0;
  map{my $i = $_;
      map{$c++ if $a->[$i] eq reverse $a->[$_]}$i+1..$#$a}0..$#$a;
  $c
}

printf "%d\n", maximum_pairs(['ab','de','ed','bc']);
printf "%d\n", maximum_pairs(['aa','ba','cd','ed']);
printf "%d\n", maximum_pairs(['uv','qp','st','vu','mn','pq']);

Task2

We keep picking a character from each string alternatively until we exhaust the strings:

#!/usr/bin/env perl
use strict;
use warnings;

sub merge_strings{
  my ($res,$m,$n) = ('',length $_[0],length $_[1]);
  for(my $i = 0; $i < $m || $i < $n; ++$i){
    $res .= substr $_[0],$i,1 if $i < $m;
    $res .= substr $_[1],$i,1 if $i < $n;
  }
  $res
}

printf "%s\n",merge_strings('abcd','1234');
printf "%s\n",merge_strings('abc','12345');
printf "%s\n",merge_strings('abcde','123');

TWC255

Challenge Link

Task1

We count the characters' occurrences of the first string, and do the same thing for the second string too but this time we decrement the count or if we hit 0 (false), then we delete that hash entry, leaving us with the only odd character as the remaining key to be returned:

#!/usr/bin/env perl
use strict;
use warnings;

sub odd_character{
  my %h;
  map{++$h{$_}}split '',$_[0];
  map{--$h{$_}||delete $h{$_}}split '',$_[1];
  keys %h
}

printf "%s\n",odd_character("Perl","Preel");
printf "%s\n",odd_character("Weekly","Weeakly");
printf "%s\n",odd_character("Box","Boxy");

Task2

We count the occurrences of each word excluding the banned word, and return the one with the highest count:

#!/usr/bin/env perl
use strict;
use warnings;

sub most_frequent_word{
  my %h;
  map{$h{$_}++ if $_ ne $_[1]} split /[^\w]/,$_[0];
  (sort{$h{$b}<=>$h{$a}}keys %h)[0]
}

printf "%s\n",most_frequent_word("Joe hit a ball, the hit ball ".
				 "flew far after it was hit.",
				 "hit");
printf "%s\n",most_frequent_word("Perl and Raku belong to the same family.".
				 " Perl is the most popular language ".
				 "in the weekly challenge.",
				 "the");

TWC254

Challenge Link

Task1

First one is a math trick that we use to find out if a number is a power of 3 or not:

#!/usr/bin/env perl
use strict;
use warnings;

sub three_power{
  $_[0] == int($_[0]**(1/3))**3
}

printf "%d\n",three_power(27);
printf "%d\n",three_power(0);
printf "%d\n",three_power(6);

Task2

We reverse the list of vowels and replace them in the string, and capitalize the first letter:

#!/usr/bin/env perl
use strict;
use warnings;

sub reverse_vowels{
  my ($str) = @_;
  my @vowels = $str =~ /[aeiou]/gi;
  $str =~ s/([aeiou])/pop @vowels/egi;
  ucfirst $str
}

printf "%s\n",reverse_vowels('Raku');
printf "%s\n",reverse_vowels('Perl');
printf "%s\n",reverse_vowels('Julia');
printf "%s\n",reverse_vowels('Uiua');