Challenge 281 by Jaldhar H. Vyas.

5 files changed, 280 insertions, 0 deletions

diff --git a/challenge-281/jaldhar-h-vyas/blog.txt b/challenge-281/jaldhar-h-vyas/blog.txt
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+++ b/challenge-281/jaldhar-h-vyas/blog.txt
@@ -0,0 +1 @@
+https://www.braincells.com/perl/2024/08/perl_weekly_challenge_week_281.html
diff --git a/challenge-281/jaldhar-h-vyas/perl/ch-1.sh b/challenge-281/jaldhar-h-vyas/perl/ch-1.sh
new file mode 100755
index 0000000000..241503a868
--- /dev/null
+++ b/challenge-281/jaldhar-h-vyas/perl/ch-1.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+perl -E '$s;map{$s += ord}split//,shift; say $s%2!=1?"false":"true"' "$@"
diff --git a/challenge-281/jaldhar-h-vyas/perl/ch-2.pl b/challenge-281/jaldhar-h-vyas/perl/ch-2.pl
new file mode 100755
index 0000000000..29a58eb2c0
--- /dev/null
+++ b/challenge-281/jaldhar-h-vyas/perl/ch-2.pl
@@ -0,0 +1,140 @@
+#!/usr/bin/perl
+use v5.38;
+
+package Position;
+use Moo;
+use namespace::clean;
+use overload '==' => \&compare;
+
+has row => (
+    is => 'rw',
+);
+
+has col => (
+    is => 'rw',
+);
+
+around BUILDARGS => sub($orig, $class, @args) {
+    return { row => $args[0], col => $args[1] };
+};
+
+sub str {
+    my ($self) = @_;
+    return chr(ord('a') + $self->col) . (8 - $self->row);
+}
+
+sub compare {
+    my ($self, $other) = @_;
+    return $self->row == $other->row && $self->col == $other->col;
+}
+
+1;
+
+package main;
+
+sub estimatedCost {
+    return 1;
+}
+
+sub stepCost($position) {
+    return 1;
+}
+
+sub tryMove($position, $delta) {
+
+    my $dest = Position->new($position->row + $delta->row, $position->col + $delta->col);
+    return ($dest->row >= 0 && $dest->row < 8 && $dest->col >= 0 && $dest->col < 8)
+        ? $dest
+        : undef;
+}
+
+sub possibleMoves($position, $target) {
+
+    state @deltas = (
+        Position->new(-2, -1),
+        Position->new(-2, 1),
+        Position->new(-1, 2),
+        Position->new(1, 2),
+        Position->new(2, 1),
+        Position->new(2, -1),
+        Position->new(-1, -2),
+        Position->new(1, -2)
+    );
+
+    my @moves;
+    for my $delta (@deltas) {
+        my $move = tryMove($position, $delta);
+        if (defined $move) {
+            push @moves, $move;
+        }
+    }
+
+    @moves = sort { estimatedCost($a, $target) < estimatedCost($b, $target); } @moves;
+
+    return @moves;
+}
+
+sub search($path, $target, $cost, $bound) {
+    my $current = $path->[-1];
+
+    my $estimate = $cost + estimatedCost($current, $target);
+    if ($estimate > $bound) {
+        return $estimate;
+    }
+
+    if ($current == $target) {
+        return '-inf';
+    }
+
+    my $min = 'inf';
+
+    for my $move (possibleMoves($current, $target)) {
+        if (!grep { $_ == $move } @{$path}) {
+            push @{$path}, $move;
+            my $t = search($path, $target, $cost + stepCost($move), $bound);
+
+            if ($t == '-inf') {
+                return '-inf';
+            }
+
+            if ($t < $min) {
+                $min = $t;
+            }
+
+            pop @{$path};
+        }
+    }
+
+    return $min;
+}
+
+sub makePath($current, $target) {
+    my @path = ( $current );
+
+    my $bound = estimatedCost($current, $target);
+
+    while(1) {
+        my $t = search(\@path, $target, 0, $bound);
+
+        if ($t == '-inf') {
+            last;
+        }
+
+        # Can't solve; this shouldn't happen.
+        if ($t == 'inf') {
+            last;
+        }
+
+        $bound = $t;
+    }
+
+    return @path;
+}
+
+my ($sc, $sr) = split //, shift;
+my ($ec, $er) = split //, shift;
+
+my $start = Position->new(ord('8') - ord($sr), ord($sc) - ord('a'));
+my $end = Position->new(ord('8') - ord($er), ord($ec) - ord('a'));
+
+say scalar makePath($start, $end) - 1;
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diff --git a/challenge-281/jaldhar-h-vyas/raku/ch-1.sh b/challenge-281/jaldhar-h-vyas/raku/ch-1.sh
new file mode 100755
index 0000000000..017e624b15
--- /dev/null
+++ b/challenge-281/jaldhar-h-vyas/raku/ch-1.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+raku -e 'say @*ARGS[0].comb.map({.ord}).sum!%%2' "$@"
diff --git a/challenge-281/jaldhar-h-vyas/raku/ch-2.raku b/challenge-281/jaldhar-h-vyas/raku/ch-2.raku
new file mode 100755
index 0000000000..051342a521
--- /dev/null
+++ b/challenge-281/jaldhar-h-vyas/raku/ch-2.raku
@@ -0,0 +1,133 @@
+#!/usr/bin/raku
+
+class Position {
+    has Int $.row is rw;
+    has Int $.col is rw;
+
+    method new( $row, $col ) {
+        self.bless(:$row, :$col);
+    }
+
+    method Str {
+        ('a'.ord + $!col).chr ~ (8 - $!row).Str;
+    }
+}
+
+multi sub infix:<==>(Position $a, Position $b) returns Bool {
+    return $a.row == $b.row && $a.col == $b.col;
+}
+
+sub estimatedCost(Position $position, Position $goal) {
+    return 1;
+}
+
+sub stepCost(Position $position) {
+    return 1;
+}
+
+
+sub tryMove(Position $position, Position $delta) {
+    my $dest = $position.clone;
+    $dest.row += $delta.row;
+    $dest.col += $delta.col;
+    return ($dest.row >= 0 && $dest.row < 8 && $dest.col >= 0 && $dest.col < 8)
+        ?? $dest
+        !! Nil;
+}
+
+sub possibleMoves(Position $position, Position $target) {
+    state @deltas = [
+        Position.new(-2, -1),
+        Position.new(-2, 1),
+        Position.new(-1, 2),
+        Position.new(1, 2),
+        Position.new(2, 1),
+        Position.new(2, -1),
+        Position.new(-1, -2),
+        Position.new(1, -2)
+    ];
+
+    my @moves;
+    for @deltas -> $delta {
+        my $move = tryMove($position, $delta);
+        if $move {
+            @moves.push($move);
+        }
+    }
+
+    @moves = @moves.sort({
+        estimatedCost($^a, $target) < estimatedCost($^b, $target);
+    });
+
+    return @moves;
+}
+
+sub search(Position @path, Position $target, Int $cost, Int $bound) {
+    my $current = @path[*-1];
+
+    my $estimate = $cost + estimatedCost($current, $target);
+    if $estimate > $bound {
+        return $estimate;
+    }
+
+    if $current == $target {
+        return -∞;
+    }
+
+    my $min = ∞;
+
+    for possibleMoves($current, $target) -> $move {
+        if $move ⊄ @path {
+            @path.push($move);
+            my $t = search(@path, $target, $cost + stepCost($move), $bound);
+
+            if $t == -∞ {
+                return -∞;
+            }
+
+            if $t < $min {
+                $min = $t;
+            }
+
+            @path.pop;
+        }
+    }
+
+    return $min;
+}
+
+sub makePath(Position $current, Position $target) {
+    my Position @path = [ $current ];
+    my $bound = estimatedCost($current, $target);
+
+    loop {
+        my $t = search(@path, $target, 0, $bound);
+
+        if $t ~~ -∞ {
+            last;
+        }
+
+        # Can't solve; this shouldn't happen.
+        if $t ~~ ∞ {
+            last;
+        }
+
+        $bound = $t;
+    }
+
+    return @path;
+}
+
+sub MAIN(
+    Str $s where  $s.chars == 2 ,
+    Str $e where $e.chars == 2
+) {
+
+    my ($sc, $sr) = $s.comb;
+    my ($ec, $er) = $e.comb;
+    my $start = Position.new('8'.ord - $sr.ord, $sc.ord - 'a'.ord );
+    my $end = Position.new('8'.ord - $er.ord, $ec.ord - 'a'.ord);
+
+    say makePath($start, $end).elems - 1;
+
+}
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