Re: Generator of integer partitionts of n

[Limbic~Region]

chiburashka,
Here is an iterative solution that produces output in ascending order and is about twice as fast as blokhead's in my rudimentary benchmarks.

#!/usr/bin/perl
use strict;
use warnings;

my $numb = $ARGV[ 0 ] || 10;
my $iter = partition( $numb );

while ( my @part = $iter->() ) {
    print "@part\n";
}

sub partition {
    my $target = shift;
    return sub { () } if ! $target || $target =~ /\D/;

    my @part = (0, (1) x ($target - 1));
    my $done = undef;

    return sub {
        return () if $done;

        my $min = $part[ -2 ];
        my $total = $part[ 0 ] ? 0 : 1;
        my $index = 0;

        for ( 0 .. $#part - 1) {
            if ( $part[ $_ ] > $min ) {
                $total += $part[ $_ ]; 
                next;
            }
            $index = $_;
            last;
        }
        $part[ $index ]++; 

        $total += $part[ $index ];
        if ( $total > $target || $part[ $index ] > $part[ 0 ] ) {
            @part = ( $index ? ++$part[ 0 ] : $part[ 0 ], (1) x ($targ
+et - $part[ 0 ]) );
        } 
        else {
            @part = ( @part[ 0 .. $index ], (1) x ($target - $total) )
+;
            push @part , 1 if $part[ 0 ] == 1;
        }

        $done = 1 if $part[ 0 ] == $target;
        return @part;
    }
}

I am sure it could probably be improved a bit more but it is working and that's what's important.