Solve PWC246

3 files changed, 33 insertions, 0 deletions

diff --git a/challenge-246/wlmb/blog.txt b/challenge-246/wlmb/blog.txt
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+https://wlmb.github.io/2023/12/03/PWC246/
diff --git a/challenge-246/wlmb/perl/ch-1.pl b/challenge-246/wlmb/perl/ch-1.pl
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+++ b/challenge-246/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 246
+# Task 1:  6 out of 49
+#
+# See https://wlmb.github.io/2023/12/03/PWC246/#task-1-6-out-of-49
+use v5.36;
+my %n=map{$_=>1} 1..49;
+my @n=keys %n;
+say join " ", @n[0..5];
diff --git a/challenge-246/wlmb/perl/ch-2.pl b/challenge-246/wlmb/perl/ch-2.pl
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+++ b/challenge-246/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 246
+# Task 2:  Linear Recurrence of Second Order
+#
+# See https://wlmb.github.io/2023/12/03/PWC246/#task-2-linear-recurrence-of-second-order
+use v5.36;
+use List::Util qw(all);
+die <<~"FIN" unless @ARGV>=4;
+    Usage: $0 N0 N1 N2 N3 [N4...]
+    to check if the sequence of integers Ni obeys a linear second order recurrence with
+    integer coefficients
+    FIN
+die "Arguments must be integer" unless all {/^[+-]?\d+$/} @ARGV;
+my @x =@ARGV;
+my $num_p = $x[2]**2-$x[3]*$x[1];
+my $num_q = $x[0]*$x[3]-$x[1]*$x[2];
+my $den = $x[0]*$x[2]-$x[1]**2;
+my $result = $num_p%$den==0 && $num_q%$den==0; # coefficients are integer
+my $p=$num_p/$den;
+my $q=$num_q/$den;
+$result &&= $x[$_]==$p*$x[$_-2]+$q*$x[$_-1] for (4..@x-1);
+$result = $result?"True":"False";
+say "@x => $result"