2nd pass with comments

2 files changed, 38 insertions, 21 deletions

diff --git a/challenge-122/james-smith/perl/ch-1.pl b/challenge-122/james-smith/perl/ch-1.pl
index c1d25b5736..e85a90e949 100644
--- a/challenge-122/james-smith/perl/ch-1.pl
+++ b/challenge-122/james-smith/perl/ch-1.pl
@@ -8,13 +8,24 @@ use Test::More;
 use Benchmark qw(cmpthese timethis);
 use Data::Dumper qw(Dumper);
 
-my @stream = map {$_*10} 1..50;
+stream( map {$_*10} 1..50 );           ## Push values into stream...
+eval {say stream_average();} until $@; ## Use eval/$@ to repeat until stream dies.
 
-say stream_average($_) foreach @stream;
+sub stream {
+  state(@stream);
+     @_      ? (push @stream,@_)       ## Parameters passed - push to stream
+   : @stream ? shift @stream           ## We have entry in stream return it
+   :           die;                    ## exhausted stream die....
+}
 
 sub stream_average {
+  ## Use state variables for the total & count;
   state($n,$t);
-  $n++; $t+=shift;
-  return $t/$n;
-}
 
+  ## Take next element and add to total
+  ## Increment the count, and return the ratio of the true values
+  ## Note we need to do pre-increment rather than
+  ## post increment so the incremement is done before use.
+
+  return ($t+=stream)/++$n;
+}
diff --git a/challenge-122/james-smith/perl/ch-2.pl b/challenge-122/james-smith/perl/ch-2.pl
index a89fd8e826..9fa94f6fb8 100644
--- a/challenge-122/james-smith/perl/ch-2.pl
+++ b/challenge-122/james-smith/perl/ch-2.pl
@@ -10,23 +10,29 @@ use Data::Dumper qw(Dumper);
 
 ## Pre-populate cache with first 3 values...
 my %cache = (
- 1 => [1],
- 2 => ['1 1',2],
- 3 => ['1 1 1','1 2','2 1',3],
+ 1 => [qw(1)],
+ 2 => [qw(11 2)],
+ 3 => [qw(111 12 21 3)],
 );
-say join "\n",@{pts(4)};
-say "";
-say join "\n",@{pts(5)};
-
+say join "\n",'',"SIZE $_",'',@{pts($_)} foreach 0..20;
+say '';
 sub pts {
-  my $n = shift;
-  return [] if $n < 1;
-  return $cache{$n} if exists $cache{$n};
-  my @res = (
-    map( {"1 $_"} @{pts($n-1)} ),
-    map( {"2 $_"} @{pts($n-2)} ),
-    map( {"3 $_"} @{pts($n-3)} )
-  );
-  return $cache{$n} = \@res;
+  ## Let's look at the first points scored - it is either
+  ## 1, 2 or 3.
+  ## So we then look to see how remaining points are scored
+  ## these are 1 - followed by all combinations for n-1
+  ##           2 - followed by all combinations for n-2
+  ##           3 - followed by all combinations for n-3
+  ## The special cases are therefore where any of these values
+  ## are less than 1 - so we need to have pre-populated values
+  ## for 1, 2 and 3 points (1; 11+2; 111+12+21+3 respectively)
+  ## We cache values as we know that we will see certain
+  ## values occuring repeatedly {e.g. the start sequences
+  ## 111, 12, 21 3 all then get all sequences for n-3
+  return $cache{$_[0]} ||= $_[0] < 1 ? [] : [
+     map( {'1'.$_} @{pts( $_[0]-1 )} ),
+     map( {'2'.$_} @{pts( $_[0]-2 )} ),
+     map( {'3'.$_} @{pts( $_[0]-3 )} )
+  ];
 }