Merge pull request #12243 from wlmb/challenges

Solve PWC327

4 files changed, 64 insertions, 0 deletions

diff --git a/challenge-327/wlmb/blog.txt b/challenge-327/wlmb/blog.txt
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+https://wlmb.github.io/2025/06/26/PWC327/
diff --git a/challenge-327/wlmb/perl/ch-1.pl b/challenge-327/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 327
+# Task 1:  Missing Integers
+#
+# See https://wlmb.github.io/2025/06/26/PWC327/#task-1-missing-integers
+use v5.36;
+die <<~"FIN" unless @ARGV;
+    Usage: $0 N1 N2..Nm
+    to find the numbers 1..m missing from N1 N2..Nm
+    FIN
+my %present;
+$present{$_}++ for @ARGV;
+say "@ARGV -> ", join " ", grep {!$present{$_}} 1..@ARGV
diff --git a/challenge-327/wlmb/perl/ch-2.pl b/challenge-327/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 327
+# Task 2:  MAD
+#
+# See https://wlmb.github.io/2025/06/26/PWC327/#task-2-mad
+use v5.36;
+die <<~"FIN" unless @ARGV>=2;
+    Usage: $0 N1 N2...
+    to find the pair of integers Ni Nj separated by
+    the minimum absolute difference.
+    FIN
+my $minimum=abs($ARGV[1]-$ARGV[0]);
+my @result;
+for my $i(0..@ARGV-1){
+    my $x=$ARGV[$i];
+    for my $j($i+1..@ARGV-1){
+	my $y=$ARGV[$j];
+	my $distance=abs($x-$y);
+	$minimum=$distance, @result=() if $distance < $minimum;
+	push @result, $x<$y? [$x,$y]:[$y,$x] if $distance==$minimum;
+    }
+}
+say "[@ARGV] -> [", (map{"[@$_]"} @result),"]"
diff --git a/challenge-327/wlmb/perl/ch-2a.pl b/challenge-327/wlmb/perl/ch-2a.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 327
+# Task 2:  MAD
+#
+# PDL version
+# See https://wlmb.github.io/2025/06/26/PWC327/#task-2-mad
+use v5.36;
+use PDL;
+use PDL::NiceSlice;
+die <<~"FIN" unless @ARGV>=2;
+    Usage: $0 A1 A2...
+    to find distinct pairs of integers [Ni Nj] taken from the array
+    Ap=[N1 N2...] separated by the minimum absolute difference.
+    The input should be in the form of strings "[N1 N2...]" which may
+    be interpreted as ndarrays by PDL.
+    FIN
+for(@ARGV){
+    my $p=pdl($_);                                                  # 1D array
+    say("Expected a 1D array: $_"), next unless $p->ndims==1;
+    my $n=$p->nelem;
+    say("Expected two or more elements: $_"), next unless $n>1;
+    my $pp=$p->dummy(0,$n);                                         # 2D array
+    my $ad=($pp-$p)->abs;                                           # abs difference
+    my $min=$ad->where($ad>0)->min;                                 # MAD
+    my $pairs=pdl($pp,$pp->mv(0,1))->whereND($ad==$min);            # select pairs
+    say "$p -> ",$pairs->whereND($pairs(:,0)<$pairs(:,1))->mv(0,1); # output distinct
+}