ch-1.raku improved

1 files changed, 28 insertions, 2 deletions

diff --git a/challenge-243/mark-anderson/raku/ch-1.raku b/challenge-243/mark-anderson/raku/ch-1.raku
index c5e9532de3..06314407da 100644
--- a/challenge-243/mark-anderson/raku/ch-1.raku
+++ b/challenge-243/mark-anderson/raku/ch-1.raku
@@ -1,13 +1,39 @@
 #!/usr/bin/env raku
 use Test;
+use Benchy;
 
 is reverse-pairs(1,3,2,3,1), 2;
 is reverse-pairs(2,4,3,5,1), 3;
 
-# I've tried memoize, race, and promises for big lists and those seem
-# to make things slower 🤔
+benchmark();
 
 sub reverse-pairs(*@a)
 {
+    my $bag = @a.BagHash;
+
+    sum gather for @a -> $n
+    { 
+        $bag{$n}--;
+
+        for $bag.keys -> $k
+        {
+            take $bag{$k} if $n > $k + $k 
+        }
+    }
+}
+
+sub reverse-pairs-slow(*@a)
+{
     + grep { .[0] > .[1] * 2 }, @a.combinations(2)
 }
+
+sub benchmark
+{
+    my @a = (1..9).roll(2500);
+
+    b 5, { reverse-pairs-slow(@a) }, { reverse-pairs(@a) }
+
+    # Old:  54.254473421s
+    # New:  1.151968905s
+    # NEW version is 47.10x faster
+}