Perl Weekly Review: Challenge

Continues from previous week.

Feel free to submit a merge request or open a ticket if you found any issues with this post. We highly appreciate and welcome your feedback.

For a quick overview, go through the original tasks and recap of the weekly challenge.

Additional feedback to our Perl Weekly Challenge’s Twitter account is much appreciated.

Task #1

Octal Number System

Write a script to print decimal number 0 to 50 in Octal Number System.

For example:

Decimal 0 = Octal 0

Decimal 1 = Octal 1

Decimal 2 = Octal 2

Decimal 3 = Octal 3

Decimal 4 = Octal 4

Decimal 5 = Octal 5

Decimal 6 = Octal 6

Decimal 7 = Octal 7

Decimal 8 = Octal 10

and so on.

Adam Russell

Adam shared the power of sprintf() in his solution.

use strict;
use warnings;
MAIN:{
    for my $x (0..50){
        print "Decimal $x = Octal " . sprintf("%o", $x) . "\n";
    }
}

Alicia Bielsa

Alicia followed similar path like Adam but used printf() instead. More compact, good job.

use strict;
use warnings;

foreach my $i ( 1..50 ) {
    printf("Decimal $i = Octal %o\n",$i);
}

Burkhard Nickels

Burkhard shared both printf() and sprintf() version. Ideal for someone new to learn Perl.

use strict;
use warnings;

# Version 1: foreach loop with printf
foreach (0 .. 50) {
    printf("Decimal: %d - Octal: %o\n",$_,$_);
}

# Version 2: map with sprintf
print my @res = map { sprintf("Dec %d - Oct %o\n",$_,$_) } (0 .. 50);

Colin Crain

Colin likes to the difficult path and manually solved the task. It reminds me my learning days.

use warnings;
use strict;
use feature ":5.26";

printf "Decimal %-2d = Octal %-2d\n", $_, octal($_) for (-50..50);

sub octal {
    my $num = shift;
    my $sign = ($num >= 0) ? "" : '-';
    $num = abs($num);
    my $out = "";
    my $rem;
    while ( $num > 0 ) {
          ($num, $rem) = (int( $num/8 ), $num % 8);
        $out = $rem . $out;
    }
    $out = $sign . $out;
    return $out ? $out : 0;  ## needs to output 0 for 0
}

Cristina Heredia

Cristina, new member of the team shared the first contribution. Looking forward to many more magical solutions.

#!/usr/bin/perl

for (my $i = 0; $i <= 50; $i++) {

    print "Decimal $i = Octal ";
    printf("%o\n",$_)for "$i";
}

Dave Jacoby

Dave also took the help from sprintf() like others. I wonder how many knows the real power of sprintf().

use feature qw{ say };
use strict;
use warnings;

for my $d ( 0 .. 50 ) {
    my $o = sprintf '%o', $d;
    say qq{Decimal $d = Octal $o};
}

Duane Powell

Duane came up with handmade complete solution.

use warnings;
use strict;
use feature qw( say );

my $decimal_no = shift;
if ($decimal_no) {
    say convert_to_octal($decimal_no);
}
else {
    for (0 .. 50) {
        say convert_to_octal($_);
    }
}

sub convert_to_octal {
    my $n = shift;
    return 0 if ($n == 0);
    my @oct;
    while ($n > 0) {
        my $remainder = $n/8 - int($n/8);
        push @oct, $remainder * 8;
        $n = int($n/8);
    }
    return join('',reverse @oct);
}

Duncan C. White

Duncan introduced bit operator in a very elegant way to solve the task. I loved it.

use v5.10;  # to get "say"
use strict;
use warnings;

die "Usage: ch-1.pl [N//50]\n" if @ARGV>1;

my $n = shift // 50;

#
# my $o = to_oct_str( $x );
#   Convert x to an octal string, eg. 8 is "10"
#
sub to_oct_str
{
    my( $x ) = @_;
    my $result = "";
    if( $x > 7 )
    {
        $result = to_oct_str( $x>>3 );
    }
    $result .= $x&7;
    return $result;
}


foreach my $x (0..$n)
{
    # convert x to octal..
    my $o = to_oct_str( $x );
    say "$x\t$o";
}

E. Choroba

Choroba didn’t try to be clever and kept it simple.

use warnings;
use strict;

printf "Decimal %d = Octal %o\n", $_, $_
    for 0 .. 50;

Fabrizio Poggi

Fabrizio also got his hand dirty while solving the task. Good job.

use strict;
use warnings;

my $x;
my $y;
my $mod;
my $oct;
my @array;

foreach $x (0..50){
    print "Decimal $x = ";
    if ($x < 8) {
        $oct = $x;
    } else {
        do {
            $y = int($x / 8);
            $mod = $x % 8;
            push (@array, $mod);
            $x = $y;
            } while ($x > 8);
        push (@array, $x);
        $oct = reverse @array;
    }
print "Octal $oct \n";
@array=();
}

Jaldhar H. Vyas

Jaldhar made it look cool with the use of map{}. Smart Cookie.

perl -e 'map { printf "Decimal %d = Octal %o\n", $_, $_ } (0 .. 50);'

Javier Luque

Javier back to basics, yet powerful.

use strict;
use warnings;
use feature qw /say/;

for my $i (1..50) {
    say 'Decimal '  . $i .
        ' = Octal ' . to_octal($i);
}

sub to_octal {
    return sprintf('%o', shift);
}

Kivanc Yazan

Kivanc also followed the straight forward path and reached the target without any issue.

use warnings;
use strict;

# Write a script to print decimal number 0 to 50 in Octal Number System.
for my $i (0..50){
  printf "Decimal %d = Octal %o\n", $i, $i;
}

Laurent Rosenfeld

Laurent one-liner is always the best, usage of **$_** twice makes it interesting.

perl -e 'printf "Decimal: %2d  =  Octal %2o \n", $_, $_ for 0..50;'

Nazareno Delucca

Nazareno solutions really hard to follow first time. I had to run the script to see the end result.

use strict;
use warnings;

my $top = shift @ARGV || 50;
my $holder = 0;

for (0..$top){
    print "dec: $_ -> oct: ". $holder++ . "\n";
    $holder+=2 if 8 == substr $holder, -1;
}

Peter Scott

Peter is a man of few words. You know why I say that, checkout his solution.

perl -E 'say sprintf "Decimal %d = Octal %o", $_, $_ for 0 .. 50'

Roger Bell_West

Roger kept it simple and easy this time.

use strict;
use warnings;

foreach (0..50) {
  printf('Decimal %d = Octal %o'."\n",$_,$_);
}

Ruben Westerberg

Ruben followed the same path like many.

perl -e 'printf "Decimal: %4d Octal: %4o\n",$_,$_ for 0..50';

Ryan Thompson

Ryan didn’t lost the path either.

printf "Decimal %2d = Octal %2o\n", $_, $_ for 0..50;

# This printf feature will be important for our Raku solution:
printf 'Decimal %1$2d = Octal %1$2o'."\n", $_ for 0..50;

Saif Ahmed

Saif is known for his documented solution. This time also it is no different.

use strict; use warnings;

my $base=8;

print "Converting from decimal to octal (base 8)\n";

for my $n (1..50){
  printf ("Decimal %2s is %2s in base %1s\n",$n, decimalTobaseN($base,$n), $base) ;
}

sub decimalTobaseN{
   my ($base,$number)=@_;                   # Function receives base and the number to convert
   my @digits=(0..9,'A'..'Z');              # potential output characters

   my $string="";                           # holds the output as string of characters

   while ($number>0){                       # continue until no more required
      my $remainder=$number % $base;        # get the remainder after division with base
      $string=$digits[$remainder].$string;  # add that to the left most side of string
      $number=($number-$remainder)/$base;   # divide the residual number by base
   }

   return $string                           # return the result
}

# The following section describes a function inverse of decimalToBaseN()
# Goal is to convert baseN string generated above back to decimal

print "\n\nPress any key to continue\n";
<STDIN>;
print "Converting decimal 100 into bases 2 to 36 and then back again\n\n";

for $base (2..36){                         # for each valid base
      my $a = decimalTobaseN($base,100);   # convert decimal 100 into that base
      my $b = baseNToDecimal($base,$a);    # then convert result back to decimal

      printf ("Decimal 100 in base %2s is %2s and converted back is %2s\n",$base, $a, $b) ;
}

sub baseNToDecimal{
   my ($base,$string)=@_;                   # Function receives base and the string to convert
   my %baseValues;                          # the base characters to decimal value are
   @baseValues{(0..9,'A'..'Z')}=(0..36);    # stored in a hash
   my $result=0;                            # initial value is zero
   foreach (split //,$string){              # go over each character in the string
                                            # multiplying result by the base before adding
       $result=$result*$base+$baseValues{$_};  # next character value to result
   }
   return $result;                          # return the result
}

Steven Wilson

Steven not only solved the task but also added handy unit test as well.

use strict;
use warnings;
use feature qw/ say /;
use Test::More tests => 1;

ok( decimal_to_octal(1792) == 3400, "test decimal 1792 is octal 3400" );

sub decimal_to_octal {
    my $dec = shift;
    my $result;
    while ( $dec > 7 ) {
        $result .= $dec % 8;
        $dec = int( $dec / 8 );
    }
    $result .= $dec;
    return scalar reverse $result;
}

for ( 0 .. 50 ) {
    say "Decimal $_ = Octal ", decimal_to_octal($_);
}

Walt Mankowski

Walt is now regular with his solutions. This time with a one-liner.

use strict;
use warnings;

printf "Decimal %d = Octal %o\n", $_, $_ for 0..50;

Wanderdoc

Wanderdoc, one of Early Bird Club members, presented the result as expected.

use strict;
use warnings FATAL => qw(all);

for my $number ( 0 .. 50 )
{
     print join(' = ', join(' ', 'Decimal', $number),
                       join(' ', 'Octal', sprintf("%o", $number))), $/;
}

Task #2

Balanced Brackets

Write a script to generate a string with random number of ( and ) brackets. Then make the script validate the string if it has balanced brackets.