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|
#!perl
################################################################################
=comment
Perl Weekly Challenge 340
=========================
TASK #1
-------
*Duplicate Removals*
Submitted by: Mohammad Sajid Anwar
You are given a string, $str, consisting of lowercase English letters.
Write a script to return the final string after all duplicate removals have been
made. Repeat duplicate removals on the given string until we no longer can.
A duplicate removal consists of choosing two adjacent and equal letters and
removing them.
Example 1
Input: $str = 'abbaca'
Output: 'ca'
Step 1: Remove 'bb' => 'aaca'
Step 2: Remove 'aa' => 'ca'
Example 2
Input: $str = 'azxxzy'
Output: 'ay'
Step 1: Remove 'xx' => 'azzy'
Step 2: Remove 'zz' => 'ay'
Example 3
Input: $str = 'aaaaaaaa'
Output: ''
Step 1: Remove 'aa' => 'aaaaaa'
Step 2: Remove 'aa' => 'aaaa'
Step 3: Remove 'aa' => 'aa'
Step 4: Remove 'aa' => ''
Example 4
Input: $str = 'aabccba'
Output: 'a'
Step 1: Remove 'aa' => 'bccba'
Step 2: Remove 'cc' => 'bba'
Step 3: Remove 'bb' => 'a'
Example 5
Input: $str = 'abcddcba'
Output: ''
Step 1: Remove 'dd' => 'abccba'
Step 2: Remove 'cc' => 'abba'
Step 3: Remove 'bb' => 'aa'
Step 4: Remove 'aa' => ''
=cut
################################################################################
#--------------------------------------#
# Copyright © 2025 PerlMonk Athanasius #
#--------------------------------------#
#===============================================================================
=comment
Interface
---------
1. If no command-line arguments are given, the test suite is run. Otherwise:
2. A single string of lowercase English letters is entered on the command-line.
=cut
#===============================================================================
use v5.38.2; # Enables strictures
use warnings;
use Const::Fast;
use Test::More;
const my $USAGE => <<END;
Usage:
perl $0 <str>
perl $0
<str> A string of lowercase English letters
END
#-------------------------------------------------------------------------------
BEGIN
#-------------------------------------------------------------------------------
{
$| = 1;
print "\nChallenge 340, Task #1: Duplicate Removals (Perl)\n\n";
}
#===============================================================================
MAIN:
#===============================================================================
{
my $argc = scalar @ARGV;
if ($argc == 0)
{
run_tests();
}
elsif ($argc == 1)
{
my $str = $ARGV[0];
$str =~ / ^ [a-z]* $ /x or error( 'Invalid input string' );
print "Input: \$str = '$str'\n";
my $no_dups = remove_duplicates( $str );
print "Output: '$no_dups'\n";
}
else
{
error( "Expected 1 or 0 command-line arguments, found $argc" );
}
}
#-------------------------------------------------------------------------------
sub remove_duplicates
#-------------------------------------------------------------------------------
{
my ($str) = @_;
1 while $str =~ s/ (.) \1 //x;
return $str;
}
#-------------------------------------------------------------------------------
sub run_tests
#-------------------------------------------------------------------------------
{
print "Running the test suite\n";
while (my $line = <DATA>)
{
chomp $line;
my ($test_name, $str, $expected) = split / \| /x, $line;
for ($test_name, $str, $expected)
{
s/ ^ \s+ //x;
s/ \s+ $ //x;
}
my $no_dups = remove_duplicates( $str );
is $no_dups, $expected, $test_name;
}
done_testing;
}
#-------------------------------------------------------------------------------
sub error
#-------------------------------------------------------------------------------
{
my ($message) = @_;
die "ERROR: $message\n$USAGE";
}
################################################################################
__DATA__
Example 1|abbaca |ca
Example 2|azxxzy |ay
Example 3|aaaaaaaa|
Example 4|aabccba |a
Example 5|abcddcba|
|
