Merge pull request #5342 from drbaggy/master

Various files

4 files changed, 132 insertions, 1 deletions

diff --git a/challenge-142/james-smith/README.md b/challenge-142/james-smith/README.md
index 33593d9731..90c0a8816c 100644
--- a/challenge-142/james-smith/README.md
+++ b/challenge-142/james-smith/README.md
@@ -1 +1,80 @@
-Solutions by James Smith
+# Perl Weekly Challenge #142
+
+You can find more information about this weeks, and previous weeks challenges at:
+
+  https://theweeklychallenge.org/
+
+If you are not already doing the challenge - it is a good place to practise your
+**perl** or **raku**. If it is not **perl** or **raku** you develop in - you can
+submit solutions in whichever language you feel comfortable with.
+
+You can find the solutions here on github at:
+
+https://github.com/drbaggy/perlweeklychallenge-club/tree/master/challenge-142/james-smith/perl
+
+# Challenge 1 - Divisor Last Digit
+
+***You are given positive integers, `$m` and `$n`.  Write a script to find total count of divisors of `$m` having last digit `$n`.***
+
+## The solution
+
+```perl
+sub divisor_last_digit {
+  my($m,$n)=@_;
+  ($n==1?1:0)+grep{$_%10==$n}
+              map{$m%$_?():$m==$_*$_?($_):($_,$m/$_)}
+              2..sqrt$m;
+}
+```
+
+ * First we find all the factors - by looping over all values between `2` and the square root of `$m`. If the value is a factor, so is `$m/$_`.
+ * We have a special case when `$m` is a square to avoid including the square root twice.
+ * We then `grep` to obtain those which have the correct last digit.
+ * There is one extra special case if `$n` is `1` we have to add `1` as `1` is a factor which we miss out in our calculations (so we don't
+   equally get `$m` as a factor).
+
+# Challenge 2 - Sleep sort
+
+***Another joke sort similar to JortSort suggested by champion Adam Russell. You are given a list of numbers. Write a script to implement Sleep Sort.***
+
+To perform a sleep sort - we loop through the list of numbers, sleeping for `$value` seconds and updating the list of results with `$value`
+
+## The solution
+
+We need to parallelise this process
+
+There are different ways of doing this `fork`, `threads`, `Promises`.
+
+We will go for the `threads` approach as it easier to implement that `Promises` but doesn't eat at memory by forking lots of times.
+
+```perl
+use threads;
+use threads::shared;
+use Time::HiRes qw(sleep);
+
+my @res :shared;
+my @list=map{0.001*int rand 3000}1..20;
+
+say "@list";
+
+sub sleeper {sleep$_[0];push@res,$_[0]}
+
+threads->new( \&sleeper, $_ ) for @list;
+
+$_->join for threads->list;
+
+say for @res;
+```
+
+## Notes
+
+ * We create a test set of 20 values between `0` and `3`.
+ * We fire off all the threads (`threads->new`)
+ * Wait for them to finish `$_->join for threads->list`
+ * Return the results.
+ * As well as `use threads`, we also `use threads::shared`. This lets us declare the results array `@res` shareable across all processes, which we need to collect the values.
+
+## Caveat
+
+Not all threads start at the same time so sometimes results don't quite come back in the same order - especially if values are close together.
+
diff --git a/challenge-142/james-smith/blog.txt b/challenge-142/james-smith/blog.txt
new file mode 100644
index 0000000000..d15115df91
--- /dev/null
+++ b/challenge-142/james-smith/blog.txt
@@ -0,0 +1 @@
+https://github.com/drbaggy/perlweeklychallenge-club/tree/master/challenge-142/james-smith
diff --git a/challenge-142/james-smith/perl/ch-1.pl b/challenge-142/james-smith/perl/ch-1.pl
new file mode 100644
index 0000000000..9964c36011
--- /dev/null
+++ b/challenge-142/james-smith/perl/ch-1.pl
@@ -0,0 +1,28 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+use Test::More;
+use Benchmark qw(cmpthese timethis);
+use Data::Dumper qw(Dumper);
+
+my @TESTS = (
+  [ 24, 2, 2 ],
+  [ 30, 5, 2 ],
+  [ 121, 1, 2 ],
+  [ 231, 1, 3 ],
+  [ 242, 1 , 3 ],
+);
+
+is( divisor_last_digit($_->[0],$_->[1]), $_->[2] ) foreach @TESTS;
+
+done_testing();
+
+sub divisor_last_digit {
+  my($m,$n)=@_;
+  ($n==1?1:0)+grep{$_%10==$n}
+              map{$m%$_?():$m==$_*$_?($_):($_,$m/$_)}
+              2..sqrt$m;
+}
diff --git a/challenge-142/james-smith/perl/ch-2.pl b/challenge-142/james-smith/perl/ch-2.pl
new file mode 100644
index 0000000000..5b7b33a428
--- /dev/null
+++ b/challenge-142/james-smith/perl/ch-2.pl
@@ -0,0 +1,23 @@
+#!/usr/local/bin/perl
+
+use strict;
+
+use warnings;
+use feature qw(say);
+
+use threads;
+use threads::shared;
+use Time::HiRes qw(sleep);
+
+my @res :shared;
+my @list=map{0.001*int rand 3000}1..20;
+
+say "@list";
+
+sub sleeper {sleep$_[0];push@res,$_[0]}
+
+threads->new( \&sleeper, $_ ) for @list;
+
+$_->join for threads->list;
+
+say for @res;