TABLE OF CONTENTS

  1. HEADLINES

  2. SPONSOR

  3. RECAP

  4. PERL REVIEW

  5. RAKU REVIEW

  6. CHART

  7. NEW MEMBERS

  8. GUESTS

  9. TASK #1: Duplicate Removals

10. TASK #2: Ascending Numbers

HEADLINES

Welcome to the Week #340 of The Weekly Challenge.

Welcome back, Torgny Lyon, and thanks for your contributions in Perl and bonus blog post.

Welcome back, Mariano Spadaccini and thanks for contributions in Elixir, Go, Perl, Python and Ruby.

Finally I found the time and energy to make a comeback and join the fun. The last time I participated was in the Week #196 (Dec, 2022). That seems like a long time, I agree. The comeback wasn’t smooth, though.

sub max_diff {
    my @nums = @_;

    # For 4 elements, there are only 3 possible pairings
    if (@nums == 4) {
        my ($a, $b, $c, $d) = @nums;
        return max(
            $a*$b - $c*$d,
            $a*$c - $b*$d,
            $a*$d - $b*$c,
        );
    }

    # For larger arrays, we need to consider extreme values
    my @s = sort {$a <=> $b} @nums;

    # The maximum difference will likely come from:
    # Option 1: (two largest) vs (two smallest)
    # Option 2: (largest*smallest) vs (second largest*second smallest)
    # Option 3: (largest*second smallest) vs (second largest*smallest)

    my $opt1 = $s[-1]*$s[-2] -  $s[0]*$s[1];
    my $opt2 = $s[-1]*$s[0]  - $s[-2]*$s[1];
    my $opt3 = $s[-1]*$s[1]  - $s[-2]*$s[0];

    return max($opt1, $opt2, $opt3);
}

As soon as I shared this on Facebook, James Smith, a fellow Team PWC member, pointed out that it would fail a few edge cases.

Normally Task #1 is supposed to be easier than Task #2 but this time it turned out to be the opposite.

This final contribution addresses the edge cases shared by James.

With this, my current rank on the leaderboard is #31. I remember, there was a time when I was in the Top 10 gang.

sub max_diff {
    my @n = @_;
    my @pairs = map {
        my $i = $_;
        map { [$i, $_, $n[$i]*$n[$_]] } $i+1 .. $#n
    } 0 .. $#n-1;

    return max
        grep { defined }
        map {
            my ($i,$j,$p1) = @$_;
            map {
                my ($k,$l,$p2) = @$_;
                ($i==$k||$i==$l||$j==$k||$j==$l) ? () : $p1-$p2
            } @pairs
        } @pairs;
}

I’ll try to find some time to share my work every week, atleast Task #1 (the easier option).

Guest contributions continue to rise and have reached a peak over the last five weeks.

The gap between guest contributions and regular contributions in Perl and Raku is getting smaller.

Python is still the most popular choice of guest languages. Having said, Rust, has now joined the 1000+ club.

However, two more, Ruby and Haskell, are very close to the target.

Happy Hacking!!

Last 5 weeks mainstream contribution stats. Thank you Team PWC for your support and encouragements.

Last 5 weeks guest contribution stats. Thank you each and every guest contributors for your time and efforts.

TOP 10 Guest Languages

Do you see your favourite language in the Top #10? If not then why not contribute regularly and make it to the top.

 1. Python     (3605)
 2. Rust       (1002)
 3. Ruby       (826)
 4. Haskell    (815)
 5. Lua        (769)
 6. C++        (651)
 7. C          (596)
 8. JavaScript (588)
 9. Go         (544)
10. BQN        (466)

Blogs with Creative Title

1. Diff Peak by Arne Sommer.

2. Sorting for the win by Bob Lied.

3. Max Complication for Min Brute Force by Matthias Muth.

4. Points? What’s the diff? by Packy Anderson.

5. Pair products, peak points by Peter Campbell Smith.

6. The Difference has Peaked by Roger Bell_West.

7. Maximum climb by Simon Green.

GitHub Repository Stats

1. Commits: 45,366 (+109)

2. Pull Requests: 12,668 (+35)

3. Contributors: 264

4. Fork: 336

5. Stars: 196

SPONSOR

With start of Week #268, we have a new sponsor Lance Wicks until the end of year 2025. Having said we are looking for more sponsors so that we can go back to weekly winner. If anyone interested please get in touch with us at perlweeklychallenge@yahoo.com. Thanks for your support in advance.

RECAP

Quick recap of The Weekly Challenge - 339 by Mohammad Sajid Anwar.

PERL REVIEW

If you missed any past reviews then please check out the collection.

RAKU REVIEW

If you missed any past reviews then please check out the collection.

CHART

Please take a look at the charts showing interesting data.

I would like to THANK every member of the team for their valuable suggestions. Please do share your experience with us.

NEW MEMBERS

Please find out How to contribute?, if you have any doubts.

Please try the excellent tool EZPWC created by respected member Saif Ahmed of Team PWC.

GUESTS

Please check out the guest contributions for the Week #339.

Please find past solutions by respected guests. Please share your creative solutions in other languages.

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' => ''

Task 2: Ascending Numbers

Submitted by: Mohammad Sajid Anwar

You are given a string, $str, is a list of tokens separated by a single space. Every token is either a positive number consisting of digits 0-9 with no leading zeros, or a word consisting of lowercase English letters.

Write a script to check if all the numbers in the given string are strictly increasing from left to right.

Example 1

Input: $str = "The cat has 3 kittens 7 toys 10 beds"
Output: true

Numbers 3, 7, 10 - strictly increasing.

Example 2

Input: $str = 'Alice bought 5 apples 2 oranges 9 bananas'
Output: false

Example 3

Input: $str = 'I ran 1 mile 2 days 3 weeks 4 months'
Output: true

Example 4

Input: $str = 'Bob has 10 cars 10 bikes'
Output: false

Example 5

Input: $str = 'Zero is 0 one is 1 two is 2'
Output: true

Last date to submit the solution 23:59 (UK Time) Sunday 28th September 2025.