Find a regular expression for strings containing the substring 01a and even number of 1's over the alphabet {0,1,a} [closed]
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28-06-2021 - |
Frage
Regular language given by its description:
The set of all strings of {0,1, a}, which contain the substring '01a' and an even number of '1'. For example, '01a1 ', '101a', '101a101'.
How to construct a regular expression that specifies the language?
Lösung
a oneliner for the heck of it:
^([0a]*1[0a]*([0a]*1[0a]*1)*)01a([0a]*1[0a]*1)*|([0a]*1[0a]*1)*01a([0a]*1[0a]*([0a]*1[0a]*1)*)$
basically, it checks for
string with odd number of 1s + 01a + string with even number of ones
OR
string with even number of 1s + 01a + string with odd number of ones
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