solution week 211-2 -- backtracking, (potentiality fast but not)

1 files changed, 41 insertions, 0 deletions

diff --git a/challenge-211/wambash/raku/ch-2.raku b/challenge-211/wambash/raku/ch-2.raku
new file mode 100644
index 0000000000..57f2b1be23
--- /dev/null
+++ b/challenge-211/wambash/raku/ch-2.raku
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+#!/usr/bin/env raku
+
+sub average  { @^a.sum / @^a.elems }
+
+sub split-same-average-reducer ( @acc, $item, :$average, :$elems-limit ) {
+    @acc
+    andthen .grep: { .elems  < $elems-limit }\
+    andthen .map:  { |@^list, $item }\
+    andthen .grep: { .&average ≤ $average     }\
+    andthen |@acc, |$_
+}
+
+sub split-same-average (+@nums) {
+    my $average = average @nums;
+    my $elems-limit = @nums.elems div 2;
+
+    @nums
+    andthen .sort
+    andthen (list(),), |$_
+    andthen .reduce: {split-same-average-reducer @^acc, $^item, :$average, :$elems-limit }\
+    andthen .first: { .&average  == $average },
+}
+
+multi MAIN (Bool :test($)!) {
+    use Test;
+    is split-same-average(1, 2, 3, 4, 5, 6, 7, 8),(4,5);
+    is split-same-average(1,3), Nil;
+    is split-same-average(<
+        44531 73257 49118 89580
+        25846 88015 19523 99285
+        75574 80036 10796 89896
+        77776 69138 75824 80610
+        47566  1623 20068  5294
+       >),
+       <10796 19523 20068 47566 69138 73257 75574 75824 80036 89896>;
+    done-testing;
+}
+
+multi MAIN (*@nums) {
+    say split-same-average @nums
+}