- Added solutions by Luca Ferrari.

- Added solutions by Robert Ransbottom.
- Added solutions by Laurent Rosenfeld.

3 files changed, 86 insertions, 0 deletions

diff --git a/challenge-281/laurent-rosenfeld/blog1.txt b/challenge-281/laurent-rosenfeld/blog1.txt
new file mode 100644
index 0000000000..a825148645
--- /dev/null
+++ b/challenge-281/laurent-rosenfeld/blog1.txt
@@ -0,0 +1 @@
+https://blogs.perl.org/users/laurent_r/2024/08/perl-weekly-challenge-281-knights-move.html
diff --git a/challenge-281/laurent-rosenfeld/perl/ch-2.pl b/challenge-281/laurent-rosenfeld/perl/ch-2.pl
new file mode 100644
index 0000000000..78b804f8bd
--- /dev/null
+++ b/challenge-281/laurent-rosenfeld/perl/ch-2.pl
@@ -0,0 +1,45 @@
+use strict;
+use warnings;
+use feature 'say';
+
+my @moves = ( [<2 1>], [<2 -1>], [<1 2>], [<1 -2>],
+              [<-1 2>], [<-1 -2>], [<-2 1>], [<-2 -1>] );
+
+sub to_coordinates {
+    my ($col, $row) = split //, shift;
+    return ord($col) - ord('a'), $row - 1;
+}
+
+sub find_shortest  {
+    my ($st_in, $end_in) = @_;
+    # convert input to Cartesian coordinates
+    my @start = to_coordinates $st_in;
+    my @end = to_coordinates $end_in;
+
+    my @to_be_explored;  # a queue of squares to be visited
+    push @to_be_explored, [0, @start];
+    my %seen = ("@start" => 1);  # already visited squares
+    while (@to_be_explored) {
+        my $node = shift @to_be_explored;
+        my ($depth, @current) = @$node;
+        return $depth if "@current" eq "@end";
+        for my $move (@moves) {
+            my @next = ( $current[0] + $move->[0],
+                         $current[1] + $move->[1] );
+            # dismiss if computed position not on chessboard
+            next if $next[0] > 7 or $next[0] < 0 or
+                    $next[1] > 7 or $next[1] < 0;
+            # dismiss if computed position already visited
+            next if exists $seen{"@next"};
+            # update seen hash and to_be_explored queue
+            $seen{"@next"} = 1;
+            push @to_be_explored, [$depth + 1, @next];
+        }
+    }
+}
+
+my @tests = ([<g2 a8>], [<g2 h2>]);
+for my $test (@tests) {
+    printf "%-6s => ", "@$test";
+    say find_shortest @$test;;
+}
diff --git a/challenge-281/laurent-rosenfeld/raku/ch-2.raku b/challenge-281/laurent-rosenfeld/raku/ch-2.raku
new file mode 100644
index 0000000000..930a2ec7fe
--- /dev/null
+++ b/challenge-281/laurent-rosenfeld/raku/ch-2.raku
@@ -0,0 +1,40 @@
+my @moves = <2 1>, <2 -1>, <1 2>, <1 -2>,
+            <-1 2>, <-1 -2>, <-2 1>, <-2 -1>;
+
+sub to-coordinates ($in) {
+    my ($col, $row) = $in.comb;
+    return $col.ord - 'a'.ord, $row - 1;
+}
+
+sub find-shortest ($st-in, $end-in) {
+    # convert input to Cartesian coordinates
+    my @start = to-coordinates $st-in;
+    my @end = to-coordinates $end-in;
+
+    my @to-be-explored;  # a queue of squares to be visited
+    push @to-be-explored, (0, @start).flat;
+    my %seen = "@start[]" => 1;  # already visited squares
+
+    while @to-be-explored {
+        my @node = shift @to-be-explored;
+        my ($depth, @current) = @node[0];
+        return $depth if "@current[]" eq "@end[]";
+        for @moves -> @move {
+            my @next = @current[0] + @move[0],
+                       @current[1] + @move[1];
+            # dismiss if computed position not on chessboard
+            next if @next.any > 7 or @next.any < 0;
+            # dismiss if computed position already visited
+            next if %seen{"@next[]"}:exists;
+            # update seen hash and to-be-explored queue
+            %seen{"@next[]"} = 1;
+            push @to-be-explored, ($depth + 1, @next).flat;
+        }
+    }
+}
+
+my @tests = <g2 a8>, <g2 h2>;
+for @tests -> @test {
+    printf "%-6s => ", "@test[]";
+    say find-shortest @test[0], @test[1];
+}