Perl - Split Array in to Smaller Evenly Distributed Arrays - arrays

Question

How would I split a Perl array of arbitrary size in to a variable number of smaller arrays with the number of elements in each smaller array being distibuted as evenly possible? The original array must not be destroyed.

Answer 1

Off the top of my head:
use strict;
use warnings;
use Data::Dumper; # for debugging only
print Dumper(distribute(7, [1..30]));
# takes number+arrayref, returns ref to array of arrays
sub distribute {
my ($n, $array) = #_;
my #parts;
my $i = 0;
foreach my $elem (#$array) {
push #{ $parts[$i++ % $n] }, $elem;
};
return \#parts;
};
This guarantees that number of elements in #parts may only differ by one. There's anonther solution that would count the numbers beforehand and use splicing:
push #parts, [ #$array[$offset..$offset+$chunk] ];
$offset += chunk;
# alter $chunk if needed.

Answer 2

Here's a version using List::MoreUtils:
use strict;
use warnings;
use List::MoreUtils qw(part);
use Data::Dumper;
my #array = 1..9;
my $partitions = 3;
my $i = 0;
print Dumper part {$partitions * $i++ / #array} #array;

Answer 3

If you don't care what winds up in each array:
use strict;
use warnings;
use List::MoreUtils qw(part);
use Data::Dumper;
my $i = 0;
my $numParts = 2;
my #part = part { $i++ % $numParts } 1 .. 30;
print Dumper #part;

Answer 4

#Dallaylaen's answer doesn't quite work because you can't pass an array into a subroutine in Perl. Instead of passing in an array (or a list as Dallaylaen did in his example) you must pass in a reference to an array:
my #arrayIn = (1..30);
my #arrayOfArrays = distribute(7, \#arrayIn);
sub distribute {
my ($n, $array) = #_;
my #parts;
my $i = 0;
foreach my $elem (#$array) {
push #{ $parts[$i++ % $n] }, $elem;
};
return #parts;
};