Beefy Boxes and Bandwidth Generously Provided by pair Networks
No such thing as a small change

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Why not to code B-Tree yourself?

#!/usr/bin/perl use strict; use warnings; my %distances = ( 100 => 'London', 200 => 'Paris', 300 => 'Rome', 600 => 'Berlin' ); my @distances = sort {$a<=>$b} keys %distances; sub make_btree { my $first = shift; my $nof = shift; if ( $nof == 1 ) { return { Value => $distances[$first] }, } else { my $m = int($nof/2); my $val = ( $distances[$first+$m-1] + $distances[$first+$m] )/ +2; return { Value => $val, Left => make_btree($first, $m), Right => make_btree($first+$m, $nof-$m), } } } my $BTREE = make_btree(0, scalar @distances); #use Data::Dumper; #print Dumper( $BTREE ); sub closest_city { my $key = shift; my $btree = $BTREE; while ( exists $btree->{Left} ) { my $v = $btree->{Value}; $btree = $btree->{ $key<$v ? 'Left' : 'Right' } } $distances{ $btree->{Value} }; } print q{closest_city(5)="}, closest_city(5), qq{"\n}; print q{closest_city(149)="}, closest_city(149), qq{"\n}; print q{closest_city(150)="}, closest_city(150), qq{"\n}; print q{closest_city(203)="}, closest_city(203), qq{"\n}; print q{closest_city(290)="}, closest_city(290), qq{"\n}; print q{closest_city(500)="}, closest_city(500), qq{"\n}; print q{closest_city(5000)="}, closest_city(5000), qq{"\n};
closest_city(5)="London" closest_city(149)="London" closest_city(150)="Paris" closest_city(203)="Paris" closest_city(290)="Rome" closest_city(500)="Berlin" closest_city(5000)="Berlin"
Following B-Tree will be generated in this example:
250 / \ 150 450 / | | \ 100 200 300 600 | | | | London Paris Rome Berlin

In reply to Re: Lookup closest hash key by nif
in thread Lookup closest hash key by Just in

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 pondering the Monastery: (6)
    As of 2020-11-24 10:22 GMT
    Find Nodes?
      Voting Booth?

      No recent polls found