josephus.pl

package Person;
# Create a new, living Person with the given position
sub new {
    my ($class, %args) = @_;
    my $self = bless { %args, alive => 1 };
    bless $self, $class;
    return $self;
}

# Create a chain of people
sub createChain {
    my ($self, $n) = @_;
    return $self unless $n > 0;
    my $succ = Person->new( position => $self->{position}+1 );
    $self->{succ} = $succ;
    $succ->createChain($n-1)
}

# Pass on the killing message
sub kill {
    my ($self, $pos, $n, $remaining) = @_;
    return $self->{succ}->kill($pos, $n, $remaining) if !$self->{alive};
    return $self if $remaining == 1;

    if ($pos == $n) {
        $self->{alive} = 0;
        $pos = 0;
        $remaining--;
    }
    $self->{succ}->kill($pos+1, $n, $remaining)
}

# Print descriptive information
sub to_s{
    my $self = shift;
    "Person #".$self->{position}.", ".($self->{alive} ? "alive" : "dead")
}

#--------------------------------------------------------------------
package main;
use strict;
use warnings;
# Circle of $n people, kill every one out of every $m
my $m = 3;
my $n = 40;

my $first = Person->new( position => 1 );
my $last = $first->createChain($n-1);
$last->{succ} = $first;

my $winner = $first->kill(1,$m,$n);
print "Winner: ", $winner->to_s, "\n";