Re^4: Generator of integer partitionts of n

[hv]

Here's a variant of the same code that stores the current partition as a packed string of bytes instead of an arrayref of integers:

  my $n = shift @ARGV;
  my $try = chr($n);
  while (defined $try) {
    print join(' ', map ord($_), split //, $try), "\n";
    $try = next_partition($try);
  }

  sub next_partition {
    my $current = shift;  # a string of bytes in descending order

    # find the last entry greater than one
    $current =~ s{ ([^\001]) (\001*) \z }{
      my $count = length($2) + 1;
      my $limit = ord($1) - 1;
      my $tail = $count % $limit;
      (chr($limit) x int(1 + $count / $limit)) . ($tail ? chr($tail) :
+ '') 
    }xe ? $current : undef;
  }

This should be rather more efficient than the arrayref variant, though obviously it can only find partitions for $n < 256.

Update: silly me, in modern perls this will do the right thing even for much larger values of $n.

Hugo