I recommend this solution.

A common error made by both beginners and experienced programmers alike is to compare arrays by, for each element in the one array, search the other array. This is OK for small amounts of data, but if the arrays have a thousand elements apiece, this is a million comparisons! (It scales quadratically.)

This is why Perl has hashes as a native data type, to make it easy to write efficient algorithms like Mirod did above. Basically whenever you find yourself thinking, "search" think about whether you can use a hash lookup instead. You cannot always, but whenever you can you will be rewarded with much faster code. (And in Perl it is often shorter as well.)

In reply to Re (tilly) 2: Double While! by tilly
in thread Double While! by Anonymous Monk

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, details, 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, summary, 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.