> in hindsight it's probably better implemented in the new coordinate system and only the results are transformed back.
> The code is much easier then.
Yep!
use strict;
use warnings;
use Data::Dump qw/pp dd/;
my $goal = [3,1,'goal'];
my $start = [0,0,'start'];
pp "OLD: ",[$start,$goal];
($start,$goal) = map old2new($_), ($start,$goal);
pp "NEW: ",[$start,$goal];
my ($gl,$gr) = @$goal;
my @results;
pathfinder( $start );
pp \@$_ for @results;
sub pathfinder {
my ( $last ) = @_;
my ( $l, $r ) = @$last ;
if ( $gl == $l and $gr == $r) {
push @results, [ map new2old($_), reverse @_ ];
return;
}
pathfinder( [$l+1,$r ,"left" ], @_ ) if $l < $gl;
pathfinder( [$l ,$r+1 ,"right"], @_ ) if $r < $gr;
}
# --------------------------------------------------
# coordinate transformations
sub old2new { # left = level - right
my ($a_old)=@_;
my @new = @$a_old;
$new[0] = $new[0] - $new[1];
return \@new;
}
sub new2old { # level = left + right
my ($a_new)=@_;
my @old = @$a_new;
$old[0] = $old[0] + $old[1];
return \@old;
}
Compilation started at Thu Mar 22 16:09:33
C:/Perl_64/bin\perl.exe d:/tmp/pascale_path.pl
("OLD: ", [[0, 0, "start"], [3, 1, "goal"]])
("NEW: ", [[0, 0, "start"], [2, 1, "goal"]])
[
[0, 0, "start"],
[1, 0, "left"],
[2, 0, "left"],
[3, 1, "right"],
]
[
[0, 0, "start"],
[1, 0, "left"],
[2, 1, "right"],
[3, 1, "left"],
]
[
[0, 0, "start"],
[1, 1, "right"],
[2, 1, "left"],
[3, 1, "left"],
]
Compilation finished at Thu Mar 22 16:09:33