use DD;
use v5.36;


# my $box = 3;
# my $l = $box*$box;
# my @s= map { 1 + int(rand($l)) } 0..($l*$l-1);

my @s = (4,3,5,2,6,9,7,8,1,
         6,8,2,5,7,1,4,9,3,
         1,9,7,8,3,4,5,6,2,
         8,2,6,1,9,5,3,4,7,
         3,7,4,6,8,2,9,1,5,
         9,5,1,7,4,3,6,2,8,
         5,1,9,3,2,6,8,7,4,
         2,4,8,9,5,7,1,3,6,
         7,6,3,4,1,8,2,5,9);

       # my @s = (1,2,3,4,5,6,7,8,9,
       #          4,5,6,5,6,7,8,9,1,
       #          7,8,9,6,7,8,9,1,2,
       #          4,5,6,7,8,9,1,2,3,
       #          5,6,7,8,9,1,2,3,4,
       #          6,7,8,9,1,2,3,4,5,
       #          7,8,9,1,2,3,4,5,6,
       #          8,9,1,2,3,4,5,6,7,
       #          9,1,2,3,4,5,6,7,8);

# my @s = map { $_ } 1..81;

# my @s = map { 0 } 0..($l * $l-1);

 print_s(@s);
 if(check_s(@s)) {
    print "valid sudoku!\n";
  } 

sub print_s {
  say scalar(@_);

  my $size = sqrt scalar @_;
  my $box = sqrt sqrt scalar @_;

  say ($size);
  say ($box);

  print "┌" . "─" x (($size * $box) + 7) . "┐\n";

  
  my $rows=0;
  for (my $x = 0; $x < scalar @_; $x+=$size) {
    $rows++;
    print "│";
    for(my $y = 0; $y < $size; $y++) {
      print " " . $_[$x+$y] . " " if $_[$x+$y] != 0;
      print " - " if $_[$x+$y] == 0;
      print " │ " if ($y + 1) % $box == 0;
    }
    print "\n";
    
    print "├" . "─" x (($size*$box)+7) . "┤\n" if ($rows % $box == 0 && $rows != $size);
 }

  print "└" . "─" x (($size * $box) + 7) . "┘\n";
}

sub check_s {

  my $size = sqrt scalar @_;
  my $box = sqrt sqrt scalar @_;

  my @correct = map { $_ } 1..$size;

  # check rows
  for(my $i = 0; $i < $size; $i++) {
    my @row = sort { $a <=> $b } uniq(get_row($i, @_));
    unless (@row ~~ @correct) {
      say "row $i is invalid";
      return 0;
    }

    my @col = sort { $a <=> $b } uniq(get_col($i, @_));
    unless (@col ~~ @correct) {
      say "col $i is invalid";
      return 0;
    }

    my @box = sort { $a <=> $b } uniq(get_box($i, @_));
    unless (@box ~~ @correct) {
      say "box $i is invalid";
      return 0;
    }
  }
  return 1;

}

sub get_col {
  my ($col, @s) = @_;

  my $size = sqrt scalar @s;
  my $box = sqrt sqrt scalar @s;

  my @col;

  @col = map { @_[($size*$_+1) + $col] } 0..$size-1;

  return @col;

}
sub get_row {

  my ($row, @s) = @_;

  my $size = sqrt scalar @s;
  my $box = sqrt sqrt scalar @s;

  my @row;

  @row = @_[$row*$size+1..($row*$size+$size)];

  return @row;

}

sub get_box {

  my ($bnum, @s) = @_;

  my $size = sqrt scalar @s;
  my $box = sqrt sqrt scalar @s;
 
  my $nboxes = $size;

  my $row = int($bnum / 3);
  my $row_start = $row*($size*3)+1;
  my $start = $row_start + (($bnum % 3)*3);


  my @box = map { my $x = $_;
    map { $s[($start+$_) + ($size*$x-1)] } 0..$box-1
  } 0..$box-1;

  return @box;
}

sub uniq {
   return do { my %seen; grep { !$seen{$_}++ } @_};
}