use strict;

sub state {
    my $c=shift;
    my $next=shift;
    my $alt=shift;
    my $visited=0;
    return {c => $c, next => $next, alt => $alt, visited => $visited};
}

sub NFA {
    my $in=shift;
    my $out=shift;
    return {in => $in, out => $out};
}

sub sym {
    my $c=shift;
    my $s=state($c, 0, 0);
    return NFA($s, $s);
}

sub dot {
    my $nfa1=shift;
    my $nfa2=shift;
    $nfa1->{out}{next}=$nfa2->{in};
    return NFA($nfa1->{in}, $nfa2->{out});
}

sub bar {
    my $nfa1=shift;
    my $nfa2=shift;
    my $s=state(256, $nfa1->{in}, $nfa2->{in});
    my $t=state(256, 0, 0);
    $nfa1->{out}{next}=$nfa2->{out}{next}=$t;
    return NFA($s, $t);
}

sub que {
    my $nfa=shift;
    my $t=state(256, 0, 0);
    my $s=state(256, $nfa->{in}, $t);
    $nfa->{out}{next}=$t;
    return NFA($s, $t);
}

sub star {
    my $nfa=shift;
    my $s=state(256, 0, $nfa->{in});
    $nfa->{out}{next}=$s;
    return NFA($s, $s);
}

sub plus {
    my $nfa=shift;
    my $s=state(256, 0, $nfa->{in});
    $nfa->{out}{next}=$s;
    return NFA($nfa->{in}, $s);
}

sub accepted {
    my $nfa=shift;
    my $s=state(257, 0, 0);
    $nfa->{out}{next}=$s;
    return NFA($nfa->{in}, $s);
}

sub __reachable {
    my $s=shift; #state
    my $list=shift; #array of states, passed by reference
    if (!$s || $s->{visited}) {
	return;
    }
    push(@{$list},$s);
    $s->{visisted}=1;
    if ($s->{c} eq 256) {
	__reachable($s->{next}, $list);
	__reachable($s->{alt}, $list);
    }
}

sub reachable {
    my $list=shift; #array of states, passed by reference
    my $v=[]; #reference to another list
    foreach my $s(@{$list}) {
	if ($s) {
	    __reachable($s, $v);
	}
    }
    foreach my $s(@{$v}) {
	$s->{visisted}=0;
    }
    return $v;
}


sub runNFA {
    my $nfa=shift; #NFA
    my $text=shift; #string
    my @a=split(//, $text); #string to array
    my $list1=[];
    my $list2=[]; #array references
    push(@{$list1}, $nfa->{in});
    $list1=reachable($list1);
    foreach my $c(@a) {
	foreach my $s(@{$list1}) {
	    if ($s->{c} eq $c || $s->{c} eq '!') {
		push(@{$list2}, $s->{next});
		if ($s->{alt}) {
		    push(@{$list2}, $s->{alt});
		}
	    }
	}
	$list1=reachable($list2); #new list
	$list2=[]; #empty
    }
    foreach my $s(@{$list1}) {
	if ($s->{c} eq 257) {
	    return 1;
	}
    }
    return 0;
}

my $nfa=accepted(
		 dot(
		     sym('a'),
		     dot(
			 star(
			      dot(
				  sym('b'),
				  sym('b')
				)
			      ),
			 sym('a')
			 )
		     )
		 );



print runNFA($nfa, "aa");