2 files changed, 85 insertions, 0 deletions
diff --git a/challenge-208/bruce-gray/raku/ch-1.raku b/challenge-208/bruce-gray/raku/ch-1.raku
new file mode 100644
index 0000000000..79649206b8
--- /dev/null
+++ b/challenge-208/bruce-gray/raku/ch-1.raku
@@ -0,0 +1,65 @@
+# Four ways-to-do-it; three use `minlist()`.
+
+# `.min` ignores ties, and `.minpairs` has no `:&by` parameter, so `minlist` is needed.
+# minlist( <foo bar baz>, :by{ .substr(1,1) } ) returns <bar baz>
+sub minlist ( @a, :&by --> List ) {
+    return @a[ @a.map(&by).minpairs».key ];
+}
+
+# Works with more than 2 lists of words!
+sub task1a ( @lists-of-words --> List ) {
+    my %word_source_index;
+    for @lists-of-words.kv -> $source, @words {
+        for      @words.kv -> $index,  $word  {
+            %word_source_index{$word}{$source} //= $index;
+        }
+    }
+
+    return %word_source_index.grep({ .value.elems == @lists-of-words.elems }).&minlist( :by{ .value.values.sum } )».key;
+}
+
+sub task1b ( @words1, @words2 --> List ) {
+    my %word_source_index;
+    %word_source_index{.value}<1> //= .key for @words1.pairs;
+    %word_source_index{.value}<2> //= .key for @words2.pairs;
+
+    return %word_source_index.grep({ .value.elems == 2 }).&minlist( :by{ .value.<1 2>.sum } )».key;
+}
+
+sub task1c ( @words1, @words2 --> List ) {
+    # Reversed to preserve the *first* index of any word duplicated in either array.
+    my %h1 = @words1.antipairs.reverse;
+    my %h2 = @words2.antipairs.reverse;
+
+    return ( %h1 ∩ %h2 ).keys.&minlist( :by{ %h1{$_} + %h2{$_} } );
+}
+
+# Crazy-efficient for early matches, but O(N²) for worst case.
+# Instead of `$sum=$i+$j`, this algorithm uses `$j=$sum-$i`.
+sub task1d ( @words1, @words2 --> List ) {
+    for @words1.keys -> $sum {
+        my @r = gather for @words1.head($sum+1).kv -> $i, $word1 {
+            my $j     = $sum - $i;
+            my $word2 = @words2[$j];
+
+            take $word1 if $word1 eq $word2;
+        }
+        return @r if @r;
+    }
+    return Empty;
+}
+
+
+constant @tests =
+    ( (<Perl Raku Love> , <Raku Perl Hate> ) , <Perl Raku> ),
+    ( ( <A B C>         , <D E F>          ) , List.new    ),
+    ( ( <A B C>         , <C A B>          ) , ('A',)      ),
+;
+use Test;
+plan 4 * +@tests;
+for @tests -> ( $in, $expected ) {
+    is-deeply task1a($in             ).sort, $expected;
+    is-deeply task1b($in.[0], $in.[1]).sort, $expected;
+    is-deeply task1c($in.[0], $in.[1]).sort, $expected;
+    is-deeply task1d($in.[0], $in.[1]).sort, $expected;
+}
diff --git a/challenge-208/bruce-gray/raku/ch-2.raku b/challenge-208/bruce-gray/raku/ch-2.raku
new file mode 100644
index 0000000000..dae6544055
--- /dev/null
+++ b/challenge-208/bruce-gray/raku/ch-2.raku
@@ -0,0 +1,20 @@
+sub task2 ( @ns --> List ) {
+    my @repeated = @ns.repeated;
+    my @missing  = ( (1 .. +@ns) (^) @ns ).keys.sort(+*);
+
+    return ( @repeated == 1 and @missing == 1 )
+        ?? ( @repeated.head,    @missing.head )
+        !! Nil;
+}
+
+
+constant @tests =
+    ( (1,2,2,4) , (2,3) ),
+    ( (1,2,3,4) , -1    ),
+    ( (1,2,3,3) , (3,4) ),
+;
+use Test;
+plan +@tests;
+for @tests -> ( $in, $expected ) {
+    is-deeply (task2($in) // -1), $expected;
+}