Challenge 281 solutions by Packy Anderson

  * Raku that maybe looks like Raku, but mostly like Perl
  * Perl
  * Python that definitely looks like Perl
  * Elixir (Task 1 only so far)

1 Blog post

12 files changed, 424 insertions, 1 deletions

diff --git a/challenge-281/packy-anderson/README.md b/challenge-281/packy-anderson/README.md
index 7974906632..69be440f4b 100644
--- a/challenge-281/packy-anderson/README.md
+++ b/challenge-281/packy-anderson/README.md
@@ -22,4 +22,4 @@
 
 ## Blog Post
 
-[Perl Weekly Challenge: Appear Twice, Count Once](https://packy.dardan.com/b/P_)
+[Perl Weekly Challenge: The Ultimate Test of Cerebral Fitness](https://packy.dardan.com/b/Pd)
diff --git a/challenge-281/packy-anderson/blog.txt b/challenge-281/packy-anderson/blog.txt
new file mode 100644
index 0000000000..84c5dd54ff
--- /dev/null
+++ b/challenge-281/packy-anderson/blog.txt
@@ -0,0 +1 @@
+https://packy.dardan.com/b/Pd
\ No newline at end of file
diff --git a/challenge-281/packy-anderson/blog/graphviz.dot b/challenge-281/packy-anderson/blog/graphviz.dot
new file mode 100644
index 0000000000..5651258a6a
--- /dev/null
+++ b/challenge-281/packy-anderson/blog/graphviz.dot
@@ -0,0 +1,59 @@
+digraph G {
+  node [style=filled]
+  edge [style=dashed]
+  g2 -> e3 -> c4 -> b6 -> a8  [style=solid, color=red];
+  g2 -> e1
+  g2 -> f4
+  g2 -> h4
+  e1 -> c2
+  e1 -> d3
+  e1 -> f3
+  e3 -> d1
+  e3 -> d5
+  e3 -> g4
+  e3 -> f1
+  e3 -> f5
+  f4 -> e2
+  f4 -> e6
+  f4 -> h3
+  f4 -> h5
+  f4 -> g6
+  c2 -> a1
+  c2 -> a3
+  c2 -> b4
+  c2 -> d4
+  d3 -> b2
+  d3 -> c1
+  d3 -> c5
+  d3 -> f2
+  d3 -> e5
+  f3 -> d2
+  f3 -> h2
+  f3 -> g1
+  f3 -> g5
+  c4 -> a5
+  c4 -> d6
+  d1 -> c3
+  d5 -> c7
+  d5 -> f6
+  d5 -> e7
+  g4 -> h6
+  f1 -> g3
+  f5 -> g7
+  e6 -> d8
+  e6 -> f8
+  g6 -> h8
+  a1 -> b3
+  a3 -> b1
+  a3 -> b5
+  b4 -> a2
+  b4 -> a6
+  b4 -> c6
+  b2 -> a4
+  c5 -> b7
+  c5 -> e4
+  c5 -> d7
+  f2 -> h1
+  e5 -> f7
+  g5 -> h7
+}
\ No newline at end of file
diff --git a/challenge-281/packy-anderson/blog/graphviz.png b/challenge-281/packy-anderson/blog/graphviz.png
new file mode 100644
index 0000000000..a0ec8a2060
--- /dev/null
+++ b/challenge-281/packy-anderson/blog/graphviz.png
diff --git a/challenge-281/packy-anderson/elixir/ch-1.exs b/challenge-281/packy-anderson/elixir/ch-1.exs
new file mode 100755
index 0000000000..ebf52874c3
--- /dev/null
+++ b/challenge-281/packy-anderson/elixir/ch-1.exs
@@ -0,0 +1,31 @@
+#!/usr/bin/env elixir
+
+defmodule PWC do
+  require Integer
+
+  def isLight(coordinates) do
+    letter = String.first(coordinates)
+    {num, _} = Integer.parse(String.last(coordinates))
+    cond do
+      String.contains?("aceg", letter)
+        and Integer.is_even(num) -> "true"
+      String.contains?("bdfh", letter)
+        and Integer.is_odd(num)  -> "true"
+      true -> "false"
+    end
+  end
+
+  def solution(coordinates) do
+    IO.puts("Input: $coordinates = \"#{coordinates}\"")
+    IO.puts("Output: " <> isLight(coordinates) )
+  end
+end
+
+IO.puts("Example 1:")
+PWC.solution("d3")
+
+IO.puts("\nExample 2:")
+PWC.solution("g5")
+
+IO.puts("\nExample 3:")
+PWC.solution("e6")
diff --git a/challenge-281/packy-anderson/elixir/ch-2.exs b/challenge-281/packy-anderson/elixir/ch-2.exs
new file mode 100755
index 0000000000..04b5c8529b
--- /dev/null
+++ b/challenge-281/packy-anderson/elixir/ch-2.exs
@@ -0,0 +1,20 @@
+#!/usr/bin/env elixir
+
+defmodule PWC do
+
+  def solution(ints) do
+    IO.puts("Input: @ints = (" <> Enum.join(ints, ", ") <> ")")
+    {sign, explain} = PWC.productSign(ints)
+    IO.puts("Output: " <> to_string(sign) )
+    IO.puts("\n" <> explain)
+  end
+end
+
+IO.puts("Example 1:")
+PWC.solution()
+
+IO.puts("\nExample 2:")
+PWC.solution()
+
+IO.puts("\nExample 3:")
+PWC.solution()
diff --git a/challenge-281/packy-anderson/perl/ch-1.pl b/challenge-281/packy-anderson/perl/ch-1.pl
new file mode 100755
index 0000000000..ff595d7c57
--- /dev/null
+++ b/challenge-281/packy-anderson/perl/ch-1.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/env perl
+use v5.40;
+
+sub isLight($coordinates) {
+  my ($letter, $num) = split //, $coordinates;
+  return (
+    ( ($letter =~ /[aceg]/) && ($num % 2 == 0) )
+    ||
+    ( ($letter =~ /[bdfh]/) && ($num % 2 == 1) )
+  ) ? 'true' : 'false';
+}
+
+sub solution($coordinates) {
+  say qq/Input: \$coordinates = "$coordinates"/;
+  say 'Output: ' . isLight($coordinates);
+}
+
+say "Example 1:";
+solution("d3");
+
+say "\nExample 2:";
+solution("g5");
+
+say "\nExample 3:";
+solution("e6");
diff --git a/challenge-281/packy-anderson/perl/ch-2.pl b/challenge-281/packy-anderson/perl/ch-2.pl
new file mode 100755
index 0000000000..92eeb1cbd4
--- /dev/null
+++ b/challenge-281/packy-anderson/perl/ch-2.pl
@@ -0,0 +1,81 @@
+#!/usr/bin/env perl
+use v5.40;
+
+my @knightMoveList = (
+  [-2, -1], [-2, +1], [-1, -2], [-1, +2],
+  [+2, -1], [+2, +1], [+1, -2], [+1, +2],
+);
+
+sub knightMoves($coordinates) {
+  my ($letter, $num) = split //, $coordinates;
+  my @endpoints;
+  foreach my $colRow ( @knightMoveList ) {
+    my ($col, $row) = @$colRow;
+    my $newcol = chr(ord($letter) + $col);
+    next unless $newcol ge "a" && $newcol le "h";
+    my $newrow = $num + $row;
+    next unless 1 <= $newrow <= 8;
+    push @endpoints, ($newcol . $newrow);
+  }
+  return @endpoints;
+}
+
+sub leastMoves($start, $end) {
+  # trivial case: we're already at the end point
+  return ( 0, $end ) if $start eq $end;
+
+  # Ok, we're going to need to search for a solution.
+
+  # Keep track of how many moves it takes to get to
+  # a particular position, starting at $start
+  my %moves = ( $start => 0 );
+
+  # also keep track of the path to get there
+  my %path_to = ( $start => $start );
+
+  # make a queue of starting points
+  my @queue = ( $start );
+
+  while ( @queue ) {
+    $start = shift @queue;
+
+    # figure out the valid moves that we haven't been to yet
+    my @endpoints = grep {
+      ! exists $path_to{$_}
+    } knightMoves($start);
+
+    foreach my $next ( @endpoints ) {
+      # build the path to the next endpoint
+      $path_to{$next} = $path_to{$start} . " -> $next";
+
+      # increment the number of moves it takes to get there
+      $moves{$next} = $moves{$start} + 1;
+
+      # have we arrived at our destination
+      return ( $moves{$next}, $path_to{$next} ) if $next eq $end;
+
+      # no? then push this space onto our processing queue
+      push @queue, $next;
+    }
+  }
+
+  # we can't get there from here!
+  # (only possible when the chessboard is an odd size)
+  return ( -1, "no path found" );
+}
+
+sub solution($start, $end) {
+  say qq/Input: \$start = '$start', \$end = '$end'/;
+  my ($count, $moves) = leastMoves($start, $end);
+  say 'Output: ' . $count;
+  say "\n$moves\n";
+}
+
+say "Example 1:";
+solution('g2', 'a8');
+
+say "\nExample 2:";
+solution('g2', 'h2');
+
+say "\nExample 3:";
+solution('a1', 'h8');
diff --git a/challenge-281/packy-anderson/python/ch-1.py b/challenge-281/packy-anderson/python/ch-1.py
new file mode 100755
index 0000000000..a327de57b8
--- /dev/null
+++ b/challenge-281/packy-anderson/python/ch-1.py
@@ -0,0 +1,23 @@
+#!/usr/bin/env python
+
+def isLight(coordinates):
+  letter = coordinates[0:1]
+  num = int(coordinates[1:])
+  return (
+     ( (letter in "aceg") and (num % 2 == 0) )
+     or
+     ( (letter in "bdfh") and (num % 2 == 1) )
+  )
+
+def solution(coordinates):
+    print(f'Input: $coordinates = "{coordinates}"')
+    print(f'Output: {isLight(coordinates)}')
+
+print('Example 1:')
+solution("d3")
+
+print('\nExample 2:')
+solution("g5")
+
+print('\nExample 3:')
+solution("e6")
diff --git a/challenge-281/packy-anderson/python/ch-2.py b/challenge-281/packy-anderson/python/ch-2.py
new file mode 100755
index 0000000000..f1b8803a71
--- /dev/null
+++ b/challenge-281/packy-anderson/python/ch-2.py
@@ -0,0 +1,77 @@
+#!/usr/bin/env python
+
+knightMoveList = [
+  [-2, -1], [-2, +1], [-1, -2], [-1, +2],
+  [+2, -1], [+2, +1], [+1, -2], [+1, +2],
+]
+
+def knightMoves(coordinates):
+  letter = coordinates[0:1]
+  num = int(coordinates[1:])
+  endpoints = []
+  for colRow in knightMoveList:
+    col, row = colRow
+    newcol = chr(ord(letter) + col)
+    if "a" <= newcol <= "h":
+      newrow = num + row
+      if 1 <= newrow <= 8:
+        endpoints.append(newcol + str(newrow))
+  return endpoints
+
+
+def leastMoves(start, end):
+  # trivial case: we're already at the end point
+  if start == end:
+      return ( 0, end )
+
+  # Ok, we're going to need to search for a solution.
+
+  # Keep track of how many moves it takes to get to
+  # a particular position, starting at $start
+  moves = { start: 0 }
+
+  # also keep track of the path to get there
+  path_to = { start: start }
+
+  # make a queue of starting points
+  queue = [ start ]
+
+  while ( queue ):
+    start = queue.pop(0)
+
+    # figure out the valid moves that we haven't been to yet
+    endpoints = [
+      m for m in knightMoves(start) if m not in path_to
+    ]
+
+    for next in endpoints:
+      # build the path to the next endpoint
+      path_to[next] = f'{path_to[start]} -> {next}'
+
+      # increment the number of moves it takes to get there
+      moves[next] = moves[start] + 1
+
+      # have we arrived at our destination
+      if next == end:
+        return ( moves[next], path_to[next] )
+
+      # no? then push this space onto our processing queue
+      queue.append(next)
+
+  # we can't get there from here!
+  # (only possible when the chessboard is an odd size)
+  return ( -1, "no path found" )
+
+def solution(start, end):
+    print(f'Input: $start = \'{start}\', $end = \'{end}\'')
+    count, moves = leastMoves(start, end)
+    print(f'Output: {count}\n\n{moves}\n')
+
+print('Example 1:')
+solution('g2', 'a8')
+
+print('\nExample 2:')
+solution('g2', 'h2')
+
+print('\nExample 3:')
+solution('a1', 'h8')
diff --git a/challenge-281/packy-anderson/raku/ch-1.raku b/challenge-281/packy-anderson/raku/ch-1.raku
new file mode 100755
index 0000000000..44ea131900
--- /dev/null
+++ b/challenge-281/packy-anderson/raku/ch-1.raku
@@ -0,0 +1,25 @@
+#!/usr/bin/env raku
+use v6;
+
+sub isLight($coordinates) {
+  my ($letter, $num) = $coordinates.comb;
+  return (
+    $letter.match(/<[aceg]>/) && ($num %% 2)
+    ||
+    $letter.match(/<[bdfh]>/) && !($num %% 2)
+  ) ?? 'true' !! 'false';
+}
+
+sub solution($coordinates) {
+  say qq/Input: \$coordinates = "$coordinates"/;
+  say 'Output: ' ~ isLight($coordinates);
+}
+
+say "Example 1:";
+solution("d3");
+
+say "\nExample 2:";
+solution("g5");
+
+say "\nExample 3:";
+solution("e6");
diff --git a/challenge-281/packy-anderson/raku/ch-2.raku b/challenge-281/packy-anderson/raku/ch-2.raku
new file mode 100755
index 0000000000..4ab5b7f4b1
--- /dev/null
+++ b/challenge-281/packy-anderson/raku/ch-2.raku
@@ -0,0 +1,81 @@
+#!/usr/bin/env raku
+use v6;
+
+my @knightMoveList = (
+  (-2, -1), (-2, +1), (-1, -2), (-1, +2),
+  (+2, -1), (+2, +1), (+1, -2), (+1, +2),
+);
+
+sub knightMoves($coordinates) {
+  my ($letter, $num) = $coordinates.comb;
+  my @endpoints;
+  for @knightMoveList -> @colRow {
+    my ($col, $row) = @colRow;
+    my $newcol = ($letter.ord + $col).chr;
+    next unless $newcol ge "a" && $newcol le "h";
+    my $newrow = $num + $row;
+    next unless 1 <= $newrow <= 8;
+    @endpoints.push($newcol ~ $newrow);
+  }
+  return @endpoints;
+}
+
+sub leastMoves($start is copy, $end) {
+  # trivial case: we're already at the end point
+  return ( 0, $end ) if $start eq $end;
+
+  # Ok, we're going to need to search for a solution.
+
+  # Keep track of how many moves it takes to get to
+  # a particular position, starting at $start
+  my %moves = ( $start => 0 );
+
+  # also keep track of the path to get there
+  my %path_to = ( $start => $start );
+
+  # make a queue of starting points
+  my @queue = ( $start );
+
+  while ( @queue ) {
+    $start = @queue.shift;
+
+    # figure out the valid moves that we haven't been to yet
+    my @endpoints = knightMoves($start).grep({
+      %path_to{$_}:!exists
+    });
+
+    for @endpoints -> $next {
+      # build the path to the next endpoint
+      %path_to{$next} = %path_to{$start} ~ " -> $next";
+
+      # increment the number of moves it takes to get there
+      %moves{$next} = %moves{$start} + 1;
+
+      # have we arrived at our destination
+      return ( %moves{$next}, %path_to{$next} ) if $next eq $end;
+
+      # no? then push this space onto our processing queue
+      @queue.push: $next;
+    }
+  }
+
+  # we can't get there from here!
+  # (only possible when the chessboard is an odd size)
+  return ( -1, "no path found" );
+}
+
+sub solution($start, $end) {
+  say qq/Input: \$start = '$start', \$end = '$end'/;
+  my ($count, $moves) = leastMoves($start, $end);
+  say 'Output: ' ~ $count;
+  say "\n$moves\n";
+}
+
+say "Example 1:";
+solution('g2', 'a8');
+
+say "\nExample 2:";
+solution('g2', 'h2');
+
+say "\nExample 3:";
+solution('a1', 'h8');