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Regular expressions - odd amounts, as opposed to even

  • 30-10-2011 3:14pm
    #1
    The_B_Man
    Registered Users, Registered Users 2 Posts: 7,893 ✭✭✭


    Can someone answer this for me:

    Give a regular expression for "The set of all strings of 0's and 1's having an odd number of 0's".

    The input alphabet is obviously {0,1}. I understand the question, but I just don't know how to represent an odd amount of 0's in regular expression form. I could even draw a Finite State Machine to represent it!

    Any help appreciated.
    Thanks.


Comments

  • #2
    humbert
    Registered Users, Registered Users 2 Posts: 5,238 ✭✭✭humbert


    This looks like a sufficiently similar example. Although I only took a cursory glance at it.

    I think the approach would be to create an expression to find pairs of 0s that may or may not be consecutive, then find 0 to infinitely many of them, and finally check to make sure that sequence is followed by a 0.


    I'm sure there are other approaches.


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