Regex for bit string containing at least 2 zeros but no consecutive zeros.











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This is what I have:



(1*011*011*)*



But I don't think this is accounting for an odd number of zeros, like "10101010101111". I think I have the right expression that satisfies no 2 consecutive zeros and even number of zeros.










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    up vote
    0
    down vote

    favorite












    This is what I have:



    (1*011*011*)*



    But I don't think this is accounting for an odd number of zeros, like "10101010101111". I think I have the right expression that satisfies no 2 consecutive zeros and even number of zeros.










    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      This is what I have:



      (1*011*011*)*



      But I don't think this is accounting for an odd number of zeros, like "10101010101111". I think I have the right expression that satisfies no 2 consecutive zeros and even number of zeros.










      share|cite|improve this question













      This is what I have:



      (1*011*011*)*



      But I don't think this is accounting for an odd number of zeros, like "10101010101111". I think I have the right expression that satisfies no 2 consecutive zeros and even number of zeros.







      regular-expressions






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      share|cite|improve this question










      asked Dec 3 at 19:19









      pinklemonade

      836




      836






















          1 Answer
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          I'll get you started.



          You need to have two zeroes, so start by putting those in your regex, leaving space between, before and after:



          $$
          ______0______0______
          $$

          Now, consider the space on the left. Every zero in this region is followed by a $1$. Therefore, this portion can be broken into sums of $(01)$ and $1$, so it is $(01|1)^*$:
          $$
          (01|1)^*0______0______
          $$

          What about the space in the middle? It has similar rules, but we cannot quite use the same regex $(01|1)^*$ we used on the left. The problem is that this can begin with a zero, which would cause a $00$ with the first $0$ we placed. How can you fix this?






          share|cite|improve this answer





















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            1 Answer
            1






            active

            oldest

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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            0
            down vote













            I'll get you started.



            You need to have two zeroes, so start by putting those in your regex, leaving space between, before and after:



            $$
            ______0______0______
            $$

            Now, consider the space on the left. Every zero in this region is followed by a $1$. Therefore, this portion can be broken into sums of $(01)$ and $1$, so it is $(01|1)^*$:
            $$
            (01|1)^*0______0______
            $$

            What about the space in the middle? It has similar rules, but we cannot quite use the same regex $(01|1)^*$ we used on the left. The problem is that this can begin with a zero, which would cause a $00$ with the first $0$ we placed. How can you fix this?






            share|cite|improve this answer

























              up vote
              0
              down vote













              I'll get you started.



              You need to have two zeroes, so start by putting those in your regex, leaving space between, before and after:



              $$
              ______0______0______
              $$

              Now, consider the space on the left. Every zero in this region is followed by a $1$. Therefore, this portion can be broken into sums of $(01)$ and $1$, so it is $(01|1)^*$:
              $$
              (01|1)^*0______0______
              $$

              What about the space in the middle? It has similar rules, but we cannot quite use the same regex $(01|1)^*$ we used on the left. The problem is that this can begin with a zero, which would cause a $00$ with the first $0$ we placed. How can you fix this?






              share|cite|improve this answer























                up vote
                0
                down vote










                up vote
                0
                down vote









                I'll get you started.



                You need to have two zeroes, so start by putting those in your regex, leaving space between, before and after:



                $$
                ______0______0______
                $$

                Now, consider the space on the left. Every zero in this region is followed by a $1$. Therefore, this portion can be broken into sums of $(01)$ and $1$, so it is $(01|1)^*$:
                $$
                (01|1)^*0______0______
                $$

                What about the space in the middle? It has similar rules, but we cannot quite use the same regex $(01|1)^*$ we used on the left. The problem is that this can begin with a zero, which would cause a $00$ with the first $0$ we placed. How can you fix this?






                share|cite|improve this answer












                I'll get you started.



                You need to have two zeroes, so start by putting those in your regex, leaving space between, before and after:



                $$
                ______0______0______
                $$

                Now, consider the space on the left. Every zero in this region is followed by a $1$. Therefore, this portion can be broken into sums of $(01)$ and $1$, so it is $(01|1)^*$:
                $$
                (01|1)^*0______0______
                $$

                What about the space in the middle? It has similar rules, but we cannot quite use the same regex $(01|1)^*$ we used on the left. The problem is that this can begin with a zero, which would cause a $00$ with the first $0$ we placed. How can you fix this?







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Dec 3 at 21:07









                Mike Earnest

                19.6k11950




                19.6k11950






























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