count numbers of path from 0,0 to n,m avoiding obstacles

t2q22.pl

#!/usr/bin/perl

use strict;
use warnings;

# number of paths from [0,0] to [n,m] ...
my $seed = srand(2323043460);
printf "seed: %s\n",$seed;
my ($n,$m) = (6,5);
my @A = ();
for (0 ..$m-1) {
  push @A, [ map { rand(1)>0.5?1:0; } (0 .. $n-1) ]
}
$A[0][0] = 1;
$A[$m-1][$n-1] = 1;

my $result = &hack(\@A);

sub hack {

   our @ar = @{$_[0]};
   our $m = scalar(@ar);
   our $n = scalar(@{$ar[0]});
   print "n: $n\n";
   print "m: $m\n";
   for my $j (0 .. $#ar) {
     printf "ar[%2d]: [%s]\n",$j,join(',',@{$ar[$j]});
   }
   my $res = &nbp(0,0);
   sub nbp {
     my ($x,$y) = @_;
     if ($x == $n-1 && $y == $m-1 ) { print ".\n"; return 1; }
     my ($dp,$rp) = (0,0);
     if ($ar[$y+1][$x]) { printf " v %d,%d",$x,$y+1; $dp = &nbp($x,$y+1); }
     if ($ar[$y][$x+1]) { printf " -> %s,%d",$x+1,$y; $rp = &nbp($x+1,$y); }
     my $count = $dp + $rp;
     return $count;
   }
   return $res;
}

print "$result\n";
exit $?;