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# Perl Weekly Challenge - 026
# Task #1
#
# See
# engineering.purdue.edu/~mark/pwc -026 -1. pdf
# for more information.
#
# The command line should be, for example ,
# perl6 t.p6 stones jewels
# The values for "stones" and "jewels"
# default to "chancellor" and "chocolate ".
#
#
# Run using Perl v6.d;
use v6.d;
sub MAIN($a = 'chancellor', $b = 'chocolate')
{
# Check that$a and$b consist of only upper and lowerccase letters.
($a ~~ /^^<[A..Za..z]>+$$/) or die qq/"$a" must consist of one or more letters /;
($b ~~ /^^<[A..Za..z]>+$$/) or die qq/"$a" must consist of one or more letters /;
# Convert$a and$b to arrays.
my @a =$a.comb (/./).unique;
my @b =$b.comb (/./);
#
# Array -based solution.
#
# If keys to a hash can be expressed as small
# non -negative integers you may want to use an
# array instead of a hash.
my @in -a;
@a.map({@in -a[$_.ord] = True });
$count = 0;
@b.map({@in -a[$_.ord] and $count++});
$count.say;
#
# Cross -product based solution.
#
$count = 0;
(@a X @b).map({$_[0] eq $_[1] and $count++});
$count.say;
#
# Hash -based solution.
#
# Make a %a hash with letter keys and True values.
# The letters in %a are the ones we count in$b.
my %a = @a.map({$_ => True });
# Count the characters in$b that occur in$a.
my $count = 0;
@b.map ({%a{$_} and $count++});
$count.say;
#
# Set -based solution.
#
# When I was looking up "perl6 degrees to radians" to see if there was
# a built -in Perl 6 method to do it I came across
# http :// blogs.perl.org/users/laurent_r /2019/09/
# perl -weekly -challenge -26-common -letters -and -mean -angles.html
# showing how to convert a list/array to a set.
# I like Laurent Rosenfeld's solution better than any I did above.
# The following is based on his work.
my $aset = @a.Set;
$count = @b.grep({$_ (elem) $aset }).elems;
$count.say;
}
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