Week 147. Perl solutions

7 files changed, 112 insertions, 0 deletions

diff --git a/challenge-147/abigail/perl/ch-1.pl b/challenge-147/abigail/perl/ch-1.pl
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+++ b/challenge-147/abigail/perl/ch-1.pl
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+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See https://theweeklychallenge.org/blog/perl-weekly-challenge-147
+#
+
+#
+# Run as: perl ch-1.pl
+#
+
+#
+# This is asking for the first 20 terms of A024785, which we can just
+# grab from https://oeis.org/A024785/list.
+#
+# Or we port the Python code from https://oeis.org/A024785
+#
+
+use Math::Prime::Util qw [is_prime];
+
+my @todo  = qw [2 3 5 7];
+my $count = 20;
+
+print "$_ " for @todo;
+$count -= @todo;
+
+MAIN: while (@todo) {
+    my @next;
+    for my $d (1 .. 9) {
+        foreach my $p (@todo) {
+            my $candidate = "$d$p";
+            next unless is_prime ($candidate);
+            print "$candidate ";
+            last MAIN if -- $count <= 0;
+            push @next   => $candidate;
+        }
+    }
+    @todo = @next;
+}
+
+print "\n";
diff --git a/challenge-147/abigail/perl/ch-2.pl b/challenge-147/abigail/perl/ch-2.pl
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index 0000000000..e4ed1d17e9
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+++ b/challenge-147/abigail/perl/ch-2.pl
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+#!/opt/perl/bin/perl
+
+use 5.032;
+
+use strict;
+use warnings;
+no  warnings 'syntax';
+
+use experimental 'signatures';
+use experimental 'lexical_subs';
+
+#
+# See https://theweeklychallenge.org/blog/perl-weekly-challenge-147
+#
+
+#
+# Run as: perl ch-2.pl
+#
+
+#
+# We solve this by checking every pentagon number in order to see
+# whether it can be written as a sum of two (smaller) pentagon
+# numbers. If so, if their difference is a pentagon number, we
+# have the winning pair. We'll use a hash which tracks the pentagon
+# numbers seen so far.
+#
+# To calculate the next pentagon number, we will avoid division
+# (and multiplication).
+#
+# If P (N) == N * (3 * N - 1) / 2, then
+#
+# P (N + 1) == (N + 1) * (3 * (N + 1) - 1) / 2
+#           == ((N + 1) * (3 * N + 2) / 2
+#           == (3 * N * N + 5 * N + 2) / 2
+#           == (3 * N * N - N + 6 * N + 2) / 2
+#           == (N * (3 * N - 1) / 2) + ((6 * N + 2) / 2)
+#           == P (N) + 3 * N + 1
+#           == P (N) + N + N + N + 1
+#
+
+my %pentagon;
+
+MAIN: for (;;) {
+    state $n = 0;
+    state $p = 0;
+    $pentagon {$p += $n + $n + $n ++ + 1} ++;
+
+    $_ + $_ < $p && $pentagon  {$p - $_}
+                 && $pentagon  {$p - $_ - $_}
+                 && say ("$_ ", $p - $_)
+                 && last MAIN for keys %pentagon;
+}
+
diff --git a/challenge-147/abigail/t/ctest.ini b/challenge-147/abigail/t/ctest.ini
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+++ b/challenge-147/abigail/t/ctest.ini
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+# 

+# Configuration file for running tests, using ctest.

+# See https://github.com/Abigail/Misc/blob/master/ctest

+# 

+

+[names]

+1-1 = Fixed Output

+2-1 = Fixed Output

diff --git a/challenge-147/abigail/t/input-1-1 b/challenge-147/abigail/t/input-1-1
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index 0000000000..e69de29bb2
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+++ b/challenge-147/abigail/t/input-1-1
diff --git a/challenge-147/abigail/t/input-2-1 b/challenge-147/abigail/t/input-2-1
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index 0000000000..e69de29bb2
--- /dev/null
+++ b/challenge-147/abigail/t/input-2-1
diff --git a/challenge-147/abigail/t/output-1-1.exp b/challenge-147/abigail/t/output-1-1.exp
new file mode 100644
index 0000000000..3648c94b73
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+++ b/challenge-147/abigail/t/output-1-1.exp
@@ -0,0 +1 @@
+2 3 5 7 13 17 23 37 43 47 53 67 73 83 97 113 137 167 173 197
diff --git a/challenge-147/abigail/t/output-2-1.exp b/challenge-147/abigail/t/output-2-1.exp
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index 0000000000..de3d6ccd8a
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+++ b/challenge-147/abigail/t/output-2-1.exp
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+1560090 7042750