Added answers to challenge 20. Many regexes

4 files changed, 45 insertions, 0 deletions

diff --git a/challenge-020/veesh-goldman/blog.txt b/challenge-020/veesh-goldman/blog.txt
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+++ b/challenge-020/veesh-goldman/blog.txt
@@ -0,0 +1 @@
+http://blogs.perl.org/users/veesh/2019/08/solving-two-problems.html
diff --git a/challenge-020/veesh-goldman/perl5/ch-01.sh b/challenge-020/veesh-goldman/perl5/ch-01.sh
new file mode 100755
index 0000000000..14c1ada7e3
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+++ b/challenge-020/veesh-goldman/perl5/ch-01.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+perl -pE'split / /, s/(.) \g1*/$& /gx'
diff --git a/challenge-020/veesh-goldman/perl5/ch-02.pl b/challenge-020/veesh-goldman/perl5/ch-02.pl
new file mode 100755
index 0000000000..e5ef309883
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+++ b/challenge-020/veesh-goldman/perl5/ch-02.pl
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+#! /usr/bin/env perl
+use v5.22;
+
+sub sum_of_proper_divisors {
+  #start with one, because that is always a divisor
+  my $sum = 1;
+  (1 x shift) =~ /^ (..+) \g1+ $ (?{ $sum += length $1 }) ./xg;
+  return $sum
+}
+
+sub has_amicable {
+  my $start = shift;
+  #sometimes the sum of the divisors IS the number. But that's not amicable
+  return 0 if sum_of_proper_divisors($start) == $start;
+  return $start == sum_of_proper_divisors( sum_of_proper_divisors($start) )
+}
+
+
+my $num;
+while (1) {
+  last if has_amicable(++$num);
+}
+
+say "$num, ${\sum_of_proper_divisors($num)} is your pair"
diff --git a/challenge-020/veesh-goldman/perl5/t/factors.t b/challenge-020/veesh-goldman/perl5/t/factors.t
new file mode 100644
index 0000000000..7467115a68
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+++ b/challenge-020/veesh-goldman/perl5/t/factors.t
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+use Test2::V0;
+
+
+sub sum_factors {
+  my $expansion = 1 x shift;
+  my $sum = 1;
+  $expansion =~ /^(..+) \g1+ $ (?{ $sum += length $1 }) ./xg;
+
+  return $sum
+}
+
+is sum_factors(4), 3;
+is sum_factors(220), 284;
+is sum_factors(284), 220;
+
+
+done_testing;