Independent Alleles

Author: L. Grondin

http://rosalind.info/problems/lia/

Sample input

2 1

Sample output

0.684

Source code: lia-grondilu.pl

use v6;

sub MAIN(Str $data = "2 1") {
    my ($k, $N) = $data.split(" ")ยป.Int;

    my %p =  Z=> <0 1 0>;
    for ^$k {
        %p =
            :AA(2 * [+] %p Z* <1/2 1/4 0>),
            :Aa(2 * [+] %p Z* <1/2 1/2 1/2>),
            :aa(2 * [+] %p Z* <0 1/4 1/2>),
        ;
    }
    die unless 2**$k == [+] %p.values;
    my $p = %p / 2**$k;
    $p *= $p;

    my $total = 2**$k;
    my $result = [+] map -> $i {
        (1-$p)**($total - $i)*$p**$i * binomialcoefficient( $total, $i )
    }, $N .. $total;

    say $result.fmt("%.3f");
}

sub postfix:($a) { [*] 1..$a }
sub binomialcoefficient($n, $k) {
    $n! / (($n - $k)! * $k!);
}