Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw

how to use reversehash if there are more than one keys same

by Anonymous Monk
on Sep 08, 2000 at 09:33 UTC ( #31549=categorized question: print w/replies, xml ) Need Help??
Contributed by Anonymous Monk on Sep 08, 2000 at 09:33 UTC
Q&A  > hashes


reversehash to accept a hash and return a hash where the roles of keys and vaalues are reversed. that is the key of the key of the input hash becomes the value of the output hash. if there are more than one keys in the input hash has the same value, they are connected by the symbol '|' in output

Answer: how to use reversehash if there are more than one keys same
contributed by indigo

Assuming the keys of your input hash cannot contain the '|' character. Straight forward:

sub reversehash { my $href = shift; my %h; for (keys %$href) { my $v = $href->{$_}; if (exists $h{$v}) { $h{$v} .= "|$_"; } else { $h{$v} = $_; } } return \%h; }
To impress the chicks:
sub reversehash { my %h; push @{$h{$_[0]->{$_}}}, $_ for keys %{$_[0]}; $h{$_} = join '|', @{$h{$_}} for keys %h; return \%h; }

Please (register and) log in if you wish to add an answer

  • 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 taking refuge in the Monastery: (5)
    As of 2020-02-28 21:37 GMT
    Find Nodes?
      Voting Booth?
      What numbers are you going to focus on primarily in 2020?

      Results (127 votes). Check out past polls.