Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
I've been chewing on this problem for a day now. This is clearly problem with two logical parts. Part 1 is to generate all legal mappings of N columns of data into M buckets, given the constraints that no bucket can be empty, and that the columns need to stay ordered. The second part is apply these mappings to the input data, and select a mapping that yields a "best fit."

I focused on the first part, looking for a quicker, simpler solution. I think I have one. Here it is. Given a number of columns and a number of buckets, the code below calculates all legal mappings of columns to buckets, and returns these in a hash, where the key is a printable string, and the value is an anonymous array.

{ # map columns to buckets. key is string, value is anonymous array. my %c2bMap; sub c2bMappings { my($buckets, $columns) = @_; die "bogus args" unless $buckets > 1 && $columns > $buckets; %c2bMap = (); _genFrom(0, (0) x ($columns - $buckets), 1 .. ($buckets - 1)); return \%c2bMap; } sub _genFrom { my @c2bMap = @_; return if exists $c2bMap{"@c2bMap"}; print "@c2bMap\n"; #DEBUG $c2bMap{"@c2bMap"} = \@c2bMap; foreach my $i ( 2 .. $#c2bMap ) { my $n = $c2bMap[$i] - 1; if ( $c2bMap[$i - 2] == $n && $c2bMap[$i - 1] == $n ) { local $c2bMap[$i-1] = $c2bMap[$i]; _genFrom(@c2bMap); } } } } c2bMappings(4,6); __END__ 0 0 0 1 2 3 0 0 1 1 2 3 0 1 1 1 2 3 0 1 1 2 2 3 0 1 2 2 2 3 0 1 2 2 3 3 0 1 2 3 3 3 0 1 1 2 3 3 0 0 1 2 2 3 0 0 1 2 3 3
Recursion only happens with valid mappings. Note the selective localization of an element of the array that the code is about to recurse on.

In reply to Re: Puzzle: need a more general algorithm by dws
in thread Puzzle: need a more general algorithm by Ovid

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others avoiding work at the Monastery: (4)
    As of 2015-11-29 17:26 GMT
    Find Nodes?
      Voting Booth?

      What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

      Results (751 votes), past polls