From d0502ea7a89dbcc2eaeba364c81cc5aba7b83304 Mon Sep 17 00:00:00 2001
From: Util <bruce.gray@acm.org>
Date: Sun, 17 Dec 2023 15:07:18 -0600
Subject: Add TWC 247 solutions by Bruce Gray (in Raku only).

---
 challenge-247/bruce-gray/raku/ch-1.raku | 90 +++++++++++++++++++++++++++++++++
 challenge-247/bruce-gray/raku/ch-2.raku | 16 ++++++
 2 files changed, 106 insertions(+)
 create mode 100644 challenge-247/bruce-gray/raku/ch-1.raku
 create mode 100644 challenge-247/bruce-gray/raku/ch-2.raku

diff --git a/challenge-247/bruce-gray/raku/ch-1.raku b/challenge-247/bruce-gray/raku/ch-1.raku
new file mode 100644
index 0000000000..c043e2d732
--- /dev/null
+++ b/challenge-247/bruce-gray/raku/ch-1.raku
@@ -0,0 +1,90 @@
+# This code is a hot mess, and lots of corner cases are not covered.
+# Also, the task examples showed mutual (paired) exchange,
+# but that is not how Secret Santa is usually played,
+# so I have a boolean PAIR flag for that.
+
+use Adverb::Eject;
+# constant $PAIR = True;
+constant $PAIR = False;
+
+proto     task1 ( |          ) { * }
+multi sub task1 ( @n where 0 ) { Empty }
+multi sub task1 ( @n where 1 ) { @n[0] => @n[0] }
+multi sub task1 ( @n where 2 ) { @n[0] => @n[1],
+                                 @n[1] => @n[0] }
+multi sub task1 ( @n where 3 ) { @n[0] => @n[1],
+                                 @n[1] => @n[2],
+                                 @n[2] => @n[0] }
+
+multi sub task1 (@names) {
+    my @c = @names.classify(*.words[1]).map({ .value.pick(*).Array }).pick(*).flat;
+
+    my @ret;
+    if @c.elems !%% 2 {
+        my $first = @c.shift;
+        my $last  = @c.pop;
+        my $half  = @c.end div 2;
+        my $mid   = @c[$half];      @c[$half]:eject;
+
+        @ret.append: |samewith([$first, $mid, $last]);
+    }
+
+    # @n.elems is now even.
+    @ret.append: |pair_or_chain(@c);
+
+    return @ret;
+}
+sub pair_or_chain ( @names ) {
+    die unless @names %% 2;
+
+    # @a is passed in grouped order.
+    # By creating with pairings half-the-size-of-the-list distance away,
+    # we minimize the number of inter-group pairings
+    my $half = @names.elems div 2;
+    my @a = @names.head($half);
+    my @b = @names.tail($half);
+
+    return |(@a Z=> @b), |(@b Z=> @a) if $PAIR;
+
+    my @cycle = (@a Z @b).flat;
+    push @cycle, @a.head;
+
+    return @cycle.rotor(2 => -1).map({ .[0] => .[1] });
+}
+my @examples =
+  (
+    'Mr. Wall',
+    'Mrs. Wall',
+    'Mr. Anwar',
+    'Mrs. Anwar',
+    'Mr. Conway',
+    'Mr. Cross',
+  ),
+  (
+    'Mr. Wall',
+    'Mrs. Wall',
+    'Mr. Anwar',
+  ),
+  # Example from Peter Campbell Smith
+  (
+    'Rudolph Reindeer',
+    'Dasher Reindeer',
+    'Dancer Reindeer',
+    'Prancer Reindeer',
+    'Vixen Reindeer',
+    'Comet Reindeer',
+    'Cupid Reindeer',
+    'Donner Reindeer',
+    'Blitzen Reindeer',
+    'Santa Claus',
+    'Mrs. Claus',
+    'Subordinate Claus',
+  ),
+;
+
+# XXX Not really testing this time, just exercising the examples.
+# use Test; plan @tests;
+for @examples -> @names {
+    say '';
+    .say for task1(@names);
+}
diff --git a/challenge-247/bruce-gray/raku/ch-2.raku b/challenge-247/bruce-gray/raku/ch-2.raku
new file mode 100644
index 0000000000..d7c99ebf1c
--- /dev/null
+++ b/challenge-247/bruce-gray/raku/ch-2.raku
@@ -0,0 +1,16 @@
+sub task2 ( Str $s --> Str ) {
+    return $s.comb.rotor(2 => -1)».join.Bag.maxpairs».key.min;
+
+    # Or, use the min-of-negative trick to remove `.maxpairs».key` :
+    # return $s.comb.rotor(2 => -1)».join.Bag.min({ -.value, .key }).key;
+}
+
+
+my @tests =
+    <bc abcdbca>,
+    <ab cdeabeabfcdfabgcd>,
+;
+use Test; plan @tests;
+for @tests -> ($expected, $in) {
+    is task2($in), $expected, $in;
+}
-- 
cgit