cache solution, a bit late

1 files changed, 70 insertions, 0 deletions

diff --git a/challenge-049/southpawgeek/ch-2.pl b/challenge-049/southpawgeek/ch-2.pl
new file mode 100644
index 0000000000..a1ee43cbb2
--- /dev/null
+++ b/challenge-049/southpawgeek/ch-2.pl
@@ -0,0 +1,70 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+use feature qw/say/;
+
+my $cap = 3;
+($cap) = @ARGV if @ARGV;
+die "$cap isn't an int! \n" if $cap =~ /\D/;
+
+say "ok, capacity set to $cap";
+
+my @keys;
+my %cache;
+
+set(1,3);
+set(2,5);
+set(3,7);
+say get(2), "\n";
+say get(1), "\n";
+say get(4), "\n";
+set(4,9);
+say get(3), "\n";
+set(5,11);
+say get(2), "\n";
+
+sub set{
+    my ($key, $val) = @_;
+
+    # remove oldest element if we're full
+    if (scalar @keys >= $cap) {
+        my $discard = shift @keys if scalar @keys >= $cap;
+        say "discarded oldest cache data with key $discard";
+        delete $cache{$discard};      
+    }
+
+    # push returns number of elements, so subtract 1
+    my $index = (push @keys, $key) - 1;
+
+    # populate the cache
+    $cache{$key} = {'value' => $val, 'index' => $index};
+    say "added $key, $val at index $index";
+
+    say "LRU @keys MRU\n";
+}
+
+sub get{
+    my $key = shift;
+    say "getting value for key $key...";
+
+    my $val = $cache{$key}->{'value'} || undef;
+    say "$key isn't there" and return -1 unless $val;
+
+    my $index = $cache{$key}->{'index'};
+    say "found $key, $val at index $index";
+
+    my $removed = splice @keys, $index, 1;
+    say "removed $removed from index $index";
+
+    push @keys, $key;
+
+    # this will be number of elements - 1 unless something has gone wrong
+    $index = scalar @keys - 1;
+    say "MRU key $key is now indexed at $index";
+
+    # also update the cache index
+    $cache{$key}->{'index'} = $index;
+    
+    say "LRU @keys MRU";
+    return $val;
+}
\ No newline at end of file