Dear Monks,

Let's assume that I have a file called bit.txt : 
bit.txt
=====================
110101010110111010101
100000000000000000001
101010101010101010101
110000000000000000011
110100000000000000000
11

[download]
And I want two things.

1) The regular expression that matches the lines containing an even number of 1s.
2) The regular expression that matches the lines containing an odd number of 1s.

My answer for these: 
1) ^(0*10*10*)*$
2) ^(0*10*10*)*1(0*10*10*)*$

[download]
My question is: Are these the shortest possible RegExps for the job? Especially the second one? Can it be shorter?

In reply to Number of bits, length of RegExp by YAFZ

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.