Merge pull request #2079 from simongreen-net/swg-073

Challenge 73 solution by Simon

4 files changed, 71 insertions, 24 deletions

diff --git a/challenge-073/sgreen/README.md b/challenge-073/sgreen/README.md
index 6dec32d966..a272d6ba1c 100644
--- a/challenge-073/sgreen/README.md
+++ b/challenge-073/sgreen/README.md
@@ -1,39 +1,30 @@
-# Perl Weekly Challenge 072
+# Perl Weekly Challenge 073
 
 Solution by Simon Green.
 
-No solutions for last week as I was moving interstate. I'm back on board this week :)
+## TASK #1 › Min Sliding Window
 
-## TASK #1 › Trailing Zeroes
+I try not to use CPAN modules, since there is no guarantee that the user running the code has it installed. However, [List::Util](https://metacpan.org/pod/List::Util) is part of the perl core these days, so it should be safe.
 
-When you think about it, a trailing zero is a product of 10, which is 2 × 5. Forgetting about the twos (since every second number is even), the five occurs every 5 numbers. Thus the factorial from 1 to 4 will contain no trailing zeros, 5-9 one trailing zero, 10-14 three trailing zeros, and so on. Once you reach 25, it gets a little more complicated as 25 is 5 × 5. Anyway, I digress from the actual task.
+The hardest part of the challenge was taking a string and converting it into an array of integers. Originally I had `split /[^\d\-]+/`, but this didn't work as expected as the first and value would be `undef` if the first character was not a number. Nothing that a quick [search on Stack Overflow](https://stackoverflow.com/questions/2884549/how-can-i-capture-multiple-matches-from-the-same-perl-regex) doesn't fix :)
 
-For this task, I take the input, calculate the factorial value, I then use a regular expression to find the trailing zeros (if any), and then display it.
+Once the input is processed, I then work through the array and get the [minimum value](https://metacpan.org/pod/List::Util#min) for each subset of the array.
 
 ### Examples
 
-    » ./ch-1.pl 10
-    2
+    » ./ch-1.pl "(1, 5, 0, 2, 9, 3, 7, 6, 4, 8)" 3
+    0, 0, 0, 2, 3, 3, 4, 4
 
-    » ./ch-1.pl 7
-    1
+## TASK 2 › Smallest Neighbour
 
-    » ./ch-1.pl 4
-    0
+Originally I didn't understand what was required, so I reached out to Mohammad to clarify the task. In particular, I couldn't understand how the third value in the first example was '0'. I should have read the task more clearly.
 
-## TASK 2 › Lines Range
-
-This tasks was relatively simple. Read the file, skip the lines < `$A` and exit the loop once line `$B` is reached (or the end of file).
+Like with the first task, I walked through the list. If the current value was less than the previous minimum values, I would add a '0' to the result and set the new `$current_min` value. If it was not less, I would add the `$current_min` value to the result.
 
 ## Example
 
-    » ./ch-2.pl input.txt 4 12
-    L4
-    L5
-    L6
-    L7
-    L8
-    L9
-    L10
-    L11
-    L12
\ No newline at end of file
+    » ./ch-2.pl 7 8 3 10 12
+    0, 7, 0, 3, 3
+
+    » ./ch-2.pl 4 6 5
+    0, 4, 4
\ No newline at end of file
diff --git a/challenge-073/sgreen/blog.txt b/challenge-073/sgreen/blog.txt
new file mode 100644
index 0000000000..4ddb372089
--- /dev/null
+++ b/challenge-073/sgreen/blog.txt
@@ -0,0 +1 @@
+https://github.com/manwar/perlweeklychallenge-club/blob/master/challenge-073/sgreen/README.md
diff --git a/challenge-073/sgreen/perl/ch-1.pl b/challenge-073/sgreen/perl/ch-1.pl
new file mode 100755
index 0000000000..b842ec6d2f
--- /dev/null
+++ b/challenge-073/sgreen/perl/ch-1.pl
@@ -0,0 +1,30 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use List::Util 'min';
+use 5.10.1;
+
+sub main (@) {
+    my ( $string, $s ) = @_;
+
+    # Convert the first value into a list of integers
+    my @list   = ( $string =~ /(-?\d+)/g );
+    my @result = ();
+
+    # Sanity checks
+    die "The first value must be a list of intergers"  unless scalar(@list);
+    die "The second value must be a postive integer\n" unless $s =~ /^[0-9]+$/;
+    die "The second value must be at least the number of items in the list\n"
+      if $s >= scalar(@list);
+
+    # Go through the list, and calculate the minimum value
+    foreach my $i ( 0 .. scalar(@list) - $s ) {
+        push @result, min( @list[ $i .. $i + $s - 1 ] );
+    }
+
+    # Display the result
+    say join ', ', @result;
+}
+
+main(@ARGV);
diff --git a/challenge-073/sgreen/perl/ch-2.pl b/challenge-073/sgreen/perl/ch-2.pl
new file mode 100755
index 0000000000..48544a5ff9
--- /dev/null
+++ b/challenge-073/sgreen/perl/ch-2.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use 5.10.1;
+
+sub main (@) {
+    my @list        = @_;
+    my $current_min = $list[0];
+
+    my @result = (0);
+    foreach my $i ( 1 .. $#list ) {
+        if ( $list[$i] < $current_min ) {
+            push @result, 0;
+            $current_min = $list[$i];
+        }
+        else {
+            push @result, $current_min;
+        }
+    }
+
+    say join ', ', @result;
+}
+
+main(@ARGV);