a second version of 086.1

which take linear space and linear time and should be faster than v1
when @N is long.

1 files changed, 15 insertions, 4 deletions

diff --git a/challenge-086/gugod/raku/ch-1.raku b/challenge-086/gugod/raku/ch-1.raku
index 3033da1356..a1d3ea41fe 100644
--- a/challenge-086/gugod/raku/ch-1.raku
+++ b/challenge-086/gugod/raku/ch-1.raku
@@ -1,7 +1,18 @@
 
-my $A = @*ARGS.head;
-my @N = @*ARGS[1..*];
+sub v1-exists-diff-by (Num $A, @N) {
+    @N.combinations(2).first(-> @combo { $A == abs([-] @combo) });
+}
 
-my $yes = @N.combinations(2).first(-> @combo { $A == abs([-] @combo) });
+sub v2-exists-diff-by (Num $A, @N) {
+    my %pos;
+    @N.kv.map(-> $k, $v { %pos{$v}.push($k) });
+    @N.first(
+        -> $n {
+            %pos{$n + $A}:exists or %pos{$n - $A}:exists
+        });
+}
 
-say defined($yes) ?? 1 !! 0;
+my $A = @*ARGS.head.Num;
+my @N = @*ARGS[1..*].map(*.Num);
+
+say v2-exists-diff-by($A, @N) ?? 1 !! 0;