HEADLINE
No Linked List related task this week?
I am glad, this week focus was more Array/List related. Technical speaking Array and List aren’t the same in Perl. I must admit until I read the article by brian d foy, I thought they were the same. As the famous saying, you learn something new every day.
Both the tasks, this week were not terribly difficult. I noticed many members of Team PWC attempted other languages because they finished the tasks in no time. I also noticed the Trailing Zeroes task started interesting discussion on the official Twitter handle.
This week, I tried something new for unit test. I have always used Test::More for unit test ever since I started working with Perl. Recently a friend of mine Lance Wicks did a live session taking part in the weekly challenge. I watched the live video realtime. It was great experience, I must admit. During the live session, he introduced Test2::V0. It was different and interesting. As you all know, I do share unit test in addition to the regular solution. So this time, I decided to use Test2::V0 for my unit test solution.
Like last week, this time also I shared solution in Swift. Since the tasks were not difficult, I attempted both Trailing Zeroes and Line Ranges.
To add to the list, I tried Java for the first time. A friend on mine (Java Expert) on LinkedIn mentioned that he would like to solve Trim Linked List task in Java. That prompted me to brush up my Java memory. I did Java nearly 10 years ago, I took the challenge and solved the Trim Linked List.
Let me share my solutions to the Perl Weekly Challenge - 072.
TASK #1 › Trailing Zeroes
Submitted by Mohammad S Anwar
You are given a positive integer $N (<= 10).
Write a script to print number of trailing zeroes in $N!.
There were 2 parts to this task, one is compute factorial and second count trailing zeroes. I have lost count how many times I have written Perl code to compute factorial. I think this is my best solution as far as factorial computation is concerned. I love Perl regex. I don’t miss any opportunity to use it. For counting trailing zeroes, I used regex. Nothing special about the regex in this task.
sub trailing_zeroes {
my ($n) = @_;
die "ERROR: Missing number.\n"
unless defined $n;
die "ERROR: Invalid number (<= 10).\n"
if (($n <= 0) || ($n > 10));
# generate factorial
$n *= $_ for 1..$n-1;
# count trailing zeroes
$n =~ m/[1-9]?([0]+)$/;
return (defined $1)?(length($1)):(0);
}
I cheated here, if you haven’t noticed it.
I literally translated the Perl solution. The good thing about Raku is that it is very accepting. The only difference is the strange use of return statement.
sub find-trailing-zeroes(Int $N is copy where $N <= 10) {
# generate factorial
$N *= $_ for 1..$N-1;
# match trailing zeroes
my $trailing-zeroes = $N ~~ m/ <[1..9]>?(<[0]>+)$ /;
return
($trailing-zeroes)
??
($N, $trailing-zeroes[0].codes)
!!
($N, 0);
}
There is hardly anything to talk about the solution below.
use strict;
use warnings;
my $N = $ARGV[0];
print trailing_zeroes($N), "\n";
I like to experiment with Raku if I find spare time. Lets play with the one-liner solution.
Here is alternate solution:
instead of this:
say sprintf("%d => %d", $factorial, $zero-count);
I could use below:
($factorial, $zero-count).join(" => ").say;
In fact, If I am not scared, I could replace both lines with the following line.
find-trailing-zeroes($N).join(" => ").say;
Raku rocks as always.
use v6.d;
sub MAIN(Int :$N where { $N <= 10 } = 10 ) {
my ($factorial, $zero-count) = find-trailing-zeroes($N);
say sprintf("%d => %d", $factorial, $zero-count);
}
Time to talk about unit test in Perl using Test2::V0. For this I had create package TrailingZeroes. I loved the special and powerful variable $CLASS.
package TrailingZeroes;
use Moo;
sub count {
my ($self, $n) = @_;
die "ERROR: Missing number.\n"
unless defined $n;
die "ERROR: Invalid number (<= 10).\n"
if (($n <= 0) || ($n > 10));
# generate factorial
$n *= $_ for 1..$n-1;
# count trailing zeroes
$n =~ m/[1-9]?([0]+)$/;
return (defined $1)?(length($1)):(0);
}
package main;
use strict;
use warnings;
use Test2::V0 -target => 'TrailingZeroes';
my %test_cases = (
10 => 2,
9 => 1,
8 => 1,
7 => 1,
6 => 1,
5 => 1,
4 => 0,
3 => 0,
2 => 0,
1 => 0,
);
foreach my $n (sort { $a <=> $b } keys %test_cases) {
is $CLASS->count($n), $test_cases{$n}, "testing \$N=$n";
}
done_testing;
raku unit test.
use Test;
my %test-cases = (
10 => 2,
9 => 1,
8 => 1,
7 => 1,
6 => 1,
5 => 1,
4 => 0,
3 => 0,
2 => 0,
1 => 0,
);
for %test-cases.keys.sort({ $^a <=> $^b }) -> $N {
is find-trailing-zeroes($N.Int)[1],
%test-cases{$N},
"testing \$N=$N";
}
done-testing;
TASK #2 › Lines Range
Submitted by Mohammad S Anwar
You are given a text file name $file and range $A - $B where $A <= $B.
Write a script to display lines range $A and $B in the given file.
I loved the simplicity of the Perl solution below. The use of file operator makes it elegant.
sub lines_range {
my ($file, $a, $b) = @_;
die "ERROR: Invalid file [$file].\n" unless (-e $file && -f _ && -r _ && -T _);
die "ERROR: Missing A.\n" unless defined $a;
die "ERROR: Missing B.\n" unless defined $b;
die "ERROR: Invalid range [$a \- $b].\n" unless ($a <= $b);
open(my $F, "<", $file) || die "ERROR: Failed to open [$!]\n";
my @lines = <$F>;
close($F);
print $lines[$_] for --$a..--$b;
}
I don’t get to work with file when it comes to Raku. I use the weekly challenge to keep practicing it. Use of Empty is elegant. Also $file.IO is such powerful statement.
sub lines-range(Str $file, Int $A is copy, Int $B is copy) {
my @lines = Empty;
for --$A .. --$B -> $i {
@lines.push: $file.IO.lines[$i];
}
return @lines;
}
With the subroutine defined above the solution became one-liner.
use strict;
use warnings;
my $F = $ARGV[0];
my $A = $ARGV[1];
my $B = $ARGV[2];
lines_range($F, $A, $B);
With MAIN() taking care of parameter validation, the one-liner body is enough to deal with the task.
use v6.d;
sub MAIN(Str :$file where *.IO.f,
Int :$A where * > 0,
Int :$B where * >= $A) {
lines-range($file, $A, $B).join("\n").say;
}
Again using Test2::V0 for unit test and created package LinesRange.
package LinesRange;
use Moo;
sub fetch {
my ($self, $file, $a, $b) = @_;
die "ERROR: Invalid file [$file].\n"
unless (-e $file && -f _ && -r _ && -T _);
open(my $F, "<", $file) || die "ERROR: Failed to open [$!]\n";
my @lines = <$F>;
close($F);
my @ranges = ();
push @ranges, $lines[$_] for --$a..--$b;
return join "", @ranges;
}
package main;
use strict;
use warnings;
use Test2::V0 -target => 'LinesRange';
my $file = "input.txt";
my @test_cases = (
{ A => 1, B => 3, O => "L1\nL2\nL3\n" },
{ A => 2, B => 4, O => "L2\nL3\nL4\n" },
{ A => 3, B => 5, O => "L3\nL4\nL5\n" },
{ A => 4, B => 6, O => "L4\nL5\nL6\n" },
{ A => 5, B => 7, O => "L5\nL6\nL7\n" },
);
foreach my $test (@test_cases) {
is $CLASS->fetch($file, $test->{"A"}, $test->{"B"}),
$test->{"O"},
"testing A=$test->{'A'}, B=$test->{'B'}";
}
done_testing;
Raku unit is plain out of box.
use Test;
my Str $file = "input.txt";
my @test-cases = (
{ A => 1, B => 3, O => ['L1','L2','L3'] },
{ A => 2, B => 4, O => ['L2','L3','L4'] },
{ A => 3, B => 5, O => ['L3','L4','L5'] },
{ A => 4, B => 6, O => ['L4','L5','L6'] },
{ A => 5, B => 7, O => ['L5','L6','L7'] },
);
for @test-cases -> $test {
is-deeply lines-range($file, $test{<A>}, $test<B>),
$test{<O>},
"testing A=$test{<A>}, B=$test{<B>}";
}
done-testing;
That’s it for this week. Speak to you soon.