I think I have to rule the 40 character solution out of bounds on the basis of the fact that you are walking through the numbers and testing whether each is prime. This loses the central idea of Eratosthenes which is that when you find a prime you immediately mark off its multiples.

Basically you reversed the role of the 2 loops.

The 60 character answer is impressive. However it seems to scale quadratically. I must confess that I don't see why it is scaling quadratically, but it clearly is. So unless you can explain why this is a bug in Perl, I am going to have to call this a solution to only the first problem.

UPDATE
I now understand why your 60 character solution is scaling slowly. It actually scales like O(n*n/log(n)), and it is because you are walking all of the primes with each strike rather than just the multiples of the current prime. So it definitely only is a solution to the first problem.

In reply to Re (tilly) 1: (Golf): Sieve of Eratosthenes by tilly
in thread (Golf): Sieve of Eratosthenes by tilly

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.