#! perl -slw
use strict;

our $ITERS ||= 1000;
our $PICKS ||= 4;

sub genPicker {
    my $n = shift;
    my @indices = 0 .. $n - 1;
    return sub {
        return unless @indices;
        my $index = int rand @indices;
        my $choice = $indices[ $index ];
        $indices[ $index ] = $indices[ $#indices ];
        --$#indices;
        return $choice;
    };
}

my $n = 1;
my @data = map{ ( $_ ) x ( $n *=2 ) } 'A' .. 'F';

print "Required frequencies";
for my $value ( 'A' .. 'F' ) {
    printf "$value : %.1f\n", grep( { $_ eq $value } @data ) / @data * 100;
}


my %chosen;
for ( 1 .. $ITERS ) {
    my $picker = genPicker ( scalar @data );
    my %picks;

    while( keys %picks < $PICKS ) {
        my $pick = $picker->();
        my $value = $data[ $pick ];
        $picks{ $value }++ ;
    }
    $chosen{ $_ }++ for keys %picks;
}

print "\nActual frequencies:";
printf "$_ : %.1f\n", $chosen{ $_ } / ($ITERS * $PICKS) * 100
    for sort{ $chosen{ $a } <=> $chosen{ $b } } keys %chosen;