Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl-Sensitive Sunglasses
 
PerlMonks  

comment on

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

Your method (same method, but with or without subroutine) is clear and good. But if you have large data, it is too slow, because time complexity of the method is N*M. For every element from subset (M) you check all elements from list (N). For better time complexity you can use hashes (search: perldata).

#!/usr/bin/perl use warnings; use strict; use Data::Dumper; my @array = ( "APPLE", "ORANGE", "PEACH", # Use this for the O +RDER "GRAPE", "BANANA", "PINEAPPLE" ); my @subset = ( "PINEAPPLE", "GRAPE", "ORANGE", "APPLE" ); # A requir +ed subset but NOT # in the required order my @results = (); # The subset with it +s elements in the # same order as the 're +ference' array # ---- Method 2: Using hash my %indexes; my $index = 0; map { $indexes{ $_ } = $index; $index ++; } @array; printf " Index of element '$_' is: %d\n", $indexes{ $_ } for @subset; my @tmp = (); foreach my $check ( @subset ){ my( $index ) = $indexes{ $check }; push( @tmp, $index ); } my @index_list = sort {$a <=> $b} @tmp; # Sort the index values numer +ically @results = @array[@index_list]; # Slice the index items out of ' +@array' print "Method 2 (uses hash):\n"; print Dumper(@results); print "\n";
OUTPUT:
Index of element 'PINEAPPLE' is: 5 Index of element 'GRAPE' is: 3 Index of element 'ORANGE' is: 1 Index of element 'APPLE' is: 0 Method 2 (uses hash): $VAR1 = 'APPLE'; $VAR2 = 'ORANGE'; $VAR3 = 'GRAPE'; $VAR4 = 'PINEAPPLE';

In reply to Re: How to Order an Array's Elements to Match Another Array's Element Order by rsFalse
in thread How to Order an Array's Elements to Match Another Array's Element Order by ozboomer

Title:
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?
    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 making s'mores by the fire in the courtyard of the Monastery: (2)
    As of 2019-12-07 03:35 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?
      Strict and warnings: which comes first?



      Results (160 votes). Check out past polls.

      Notices?