Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

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

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


Description:

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!
  • 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
  • Outside of code tags, you may need to use entities for some characters:
            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?
    Username:
    Password:

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

    How do I use this? | Other CB clients
    Other Users?
    Others lurking in the Monastery: (13)
    As of 2014-10-21 13:12 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      For retirement, I am banking on:










      Results (103 votes), past polls