8_Queen_Problem

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my @solution = ([], [], [], [], [], [], [], []); #board

sub initial {
  for my $i (0 .. 7) {
    for (0 .. 7) {push @{$solution[$i]}, 0;} #create the board
  }
}

sub safe {
  my $row_safe = shift;
  my $col_safe = shift;
  if ($solution[$col_safe]->[$row_safe] == 0) {return 1;}
  else {return 0;}
}

sub mark {
  my $row_mark = shift;
  my $col_mark = shift;                                                              #get current col
  for my $c ($col_mark .. 7) {                                                       #from this col to the las col
    for my $r (0 .. 7) {                                                             #for each row
      if ($r == $row_mark && $c == $col_mark) {$solution[$c]->[$r] = $col_mark + 1;}
      #original answer will be marked as col+1
      elsif ($solution[$c]->[$r] == 0) {
        if ($r == $row_mark) {$solution[$c]->[$r] = 10 * ($col_mark + 1);}
        if ($r - $c == $row_mark - $col_mark) {$solution[$c]->[$r] = 10 * ($col_mark + 1);}
        if ($r + $c == $row_mark + $col_mark) {$solution[$c]->[$r] = 10 * ($col_mark + 1);}
      }#we check if the value there is 0 #we write 10* the original col+1, as attack area
      else {} # we do nothing if anything else
    }
  }
}

sub unmark {
  my $row_unmark = shift;
  my $col_unmark = shift;                                                    #get current col
  for my $c ($col_unmark .. 7) {                                             #from this col to the las col
    for my $r (0 .. 7) {                                                     #for each row
      if ($r == $row_unmark && $c == $col_unmark) {$solution[$c]->[$r] = 0;} #original answer will be marked as col+1
      elsif ($solution[$c]->[$r] == 10 * ($col_unmark + 1)) {                #we check if the value there is 0
        $solution[$c]->[$r] = 0;}
      #we write 10* the original col+1, as attack area
      else {} # we do nothing if anything else
    }
  }
}

sub solve {
  my $col_solve = shift; #for the col where we are
  if ($col_solve == 8) {
    process();
    return 1;
  }
  for my $row_solve (0 .. 7) { #for every row we are going to try
    if (safe($row_solve, $col_solve)) {
      mark($row_solve, $col_solve);
      solve($col_solve + 1);
      unmark($row_solve, $col_solve);
    }
  }
}

sub process {
  for my $rp (0 .. 7) {
    for my $cp (0 .. 7) {
      if ($solution[$rp]->[$cp] > 0 && $solution[$rp]->[$cp] < 10) {print "Q";} #create the board
      else {print "口";} #create the board
    }
    print "\n";
  }
  print "\n\n";
}

sub main {
  initial();
  solve(0);
}

main();