Merge pull request #4191 from polettix/polettix/pwc115

Add polettix's solution to challenge-115

6 files changed, 157 insertions, 0 deletions

diff --git a/challenge-115/polettix/blog.txt b/challenge-115/polettix/blog.txt
new file mode 100644
index 0000000000..ef4e04cb79
--- /dev/null
+++ b/challenge-115/polettix/blog.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2021/06/02/pwc115-string-chain/
diff --git a/challenge-115/polettix/blog1.txt b/challenge-115/polettix/blog1.txt
new file mode 100644
index 0000000000..2d8b2bdd0e
--- /dev/null
+++ b/challenge-115/polettix/blog1.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2021/06/03/pwc115-largest-multiple/
diff --git a/challenge-115/polettix/perl/ch-1.pl b/challenge-115/polettix/perl/ch-1.pl
new file mode 100644
index 0000000000..5a32d93c77
--- /dev/null
+++ b/challenge-115/polettix/perl/ch-1.pl
@@ -0,0 +1,57 @@
+#!/usr/bin/env perl
+use 5.024;
+use warnings;
+use experimental qw< postderef signatures >;
+no warnings qw< experimental::postderef experimental::signatures >;
+
+sub string_chain (@S) {
+   my $start = shift @S;
+   my ($sf, $sl) = (substr($start, 0, 1), substr($start, -1, 1));
+
+   my %starting_with;
+   push $starting_with{substr $_, 0, 1}->@*, [$_, 0] for @S;
+
+   return unless exists $starting_with{$sl};
+   my @chain = ([$starting_with{$sl}, -1]);
+
+   LINK:
+   while ('necessary') {
+      my $top = $chain[-1];
+      if ((my $i = $top->[-1]) < $top->[0]->$#*) {
+         $top->[0][$i][1] = 0 if $i >= 0; # reset last iteration
+         ++$i; # advance at least once
+         ++$i while $i <= $top->[0]->$#* && $top->[0][$i][1];
+
+         $top->[-1] = $i;
+         redo LINK if $i > $top->[0]->$#*;
+
+         my $last_letter = substr $top->[0][$i][0], -1, 1;
+         if (@chain == @S) {
+            if ($last_letter eq $sf) {
+               return [
+                  $start,
+                  map {$_->[0][$_->[-1]][0]} @chain,
+               ];
+            }
+         }
+         else {
+            $top->[0][$i][1] = 1; # mark this item
+            if (my $sw = $starting_with{$last_letter}) {
+               push @chain, [$sw, -1]; # "recurse"
+            }
+            else {
+               return if $last_letter ne $sf;
+            }
+         }
+      }
+      elsif (@chain > 1) { pop @chain } # backtrack...
+      else               { return     } # no luck...
+   }
+}
+
+my @words = @ARGV ? @ARGV : qw< abc dea cd >;
+if (my $chain = string_chain(@words)) {
+   say 1;
+   say {*STDERR} join ' ', $chain->@*;
+}
+else { say 0 }
diff --git a/challenge-115/polettix/perl/ch-2.pl b/challenge-115/polettix/perl/ch-2.pl
new file mode 100644
index 0000000000..cbe0b35928
--- /dev/null
+++ b/challenge-115/polettix/perl/ch-2.pl
@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+use 5.024;
+use warnings;
+use experimental qw< postderef signatures >;
+no warnings qw< experimental::postderef experimental::signatures >;
+
+sub largest_multiple (@N) {
+   @N = sort { $a <=> $b } @N;
+   for my $i (0 .. $#N) {
+      if ($N[$i] % 2 == 0) {
+         my ($last) = splice @N, $i, 1;
+         return join '', reverse(@N), $last;
+      }
+   }
+   return;
+}
+
+my @inputs = @ARGV ? @ARGV : qw< 1 0 2 6 >;
+say largest_multiple(@inputs);
diff --git a/challenge-115/polettix/raku/ch-1.raku b/challenge-115/polettix/raku/ch-1.raku
new file mode 100644
index 0000000000..d14468c8a5
--- /dev/null
+++ b/challenge-115/polettix/raku/ch-1.raku
@@ -0,0 +1,62 @@
+#!/usr/bin/env raku
+use v6;
+
+sub string-chain (@S is copy) {
+   my $start = @S.shift;
+   my $sf = $start.substr(0, 1);
+   my $sl = $start.substr(*-1, 1);
+
+   my %starting-with;
+   for @S -> $s {
+      %starting-with{$s.substr(0, 1)}.push([$s, 0]);
+   }
+
+   return unless %starting-with{$sl};
+   my @chain = [%starting-with{$sl}, -1],;
+
+   LINK:
+   loop {
+      my $top = @chain[*-1];
+      if (my $i = $top[*-1]) < $top[0].elems - 1 {
+         $top[0][$i][1] = 0 if $i >= 0;
+         ++$i;
+         ++$i while $i < $top[0].elems && $top[0][$i][1];
+
+         $top[1] = $i;
+         redo LINK if $i > $top[0].elems - 1;
+
+         my $last_letter = $top[0][$i][0].substr(*-1,1);
+         if (@chain.elems == @S.elems) {
+            if ($last_letter eq $sf) {
+               return [
+                  $start,
+                  @chain.map: -> $x {$x[0][$x[*-1]][0]}
+               ];
+            }
+         }
+         else {
+            $top[0][$i][1] = 1;
+            if my $sw = %starting-with{$last_letter} {
+               @chain.push: [$sw, -1];
+            }
+            else {
+               return if $last_letter ne $sf;
+            }
+         }
+      }
+      elsif (@chain.elems > 1) { @chain.pop }
+      else                     { return     }
+   }
+}
+
+sub MAIN (*@words is copy) {
+   @words = < abc dea cd > unless @words.elems;
+   my $chain = string-chain(@words);
+   if ($chain) {
+      say 1;
+      $chain.join(' ').note;
+   }
+   else {
+      say 0;
+   }
+}
diff --git a/challenge-115/polettix/raku/ch-2.raku b/challenge-115/polettix/raku/ch-2.raku
new file mode 100644
index 0000000000..5ed5755213
--- /dev/null
+++ b/challenge-115/polettix/raku/ch-2.raku
@@ -0,0 +1,17 @@
+#!/usr/bin/env raku
+use v6;
+
+sub largest-multiple (@N is copy) {
+   @N = @N.sort: {$^a leg $^b};
+   for 0 ..^ @N.elems -> $i {
+      next if @N[$i] % 2;
+      @N.unshift(@N.splice($i, 1).Slip);
+      return @N.reverse.join('');
+   }
+   return;
+}
+
+sub MAIN (*@inputs is copy) {
+   @inputs = < 1 0 2 6 > unless @inputs.elems;
+   say largest-multiple(@inputs);
+}