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how does :<br />
<br />
&nbsp;b* + b*a(ba)*<br />
<br />
satisfies my question, please explain<br />

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how does :

 b* + b*a(ba)*

satisfies my question, please explain


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The question deals with regular expression. b* + b*a(ba)* is a regular expression representation and the solution demostrates how to draw it.<br />
<br />
If you may check some reference on reading regular expression syntax.<br />
<br />
<a href="http://en.wikipedia.org/wiki/Regular_expression" rel="ugc">http://en.wikipedia.org/wiki/Regular_expression</a>
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The question deals with regular expression. b* + b*a(ba)* is a regular expression representation and the solution demostrates how to draw it.

If you may check some reference on reading regular expression syntax.

http://en.wikipedia.org/wiki/Regular_expression [http://en.wikipedia.org/wiki/Regular_expression]

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I don't understand how b* + b*a(ba)* represents each 1 in w is immediately preceded and immediately followed by a 0<br />

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I don't understand how b* + b*a(ba)* represents each 1 in w is immediately preceded and immediately followed by a 0


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if 1 is equal to b here, then one possibility that regex gives me is 1* which can be an empty string and it is not followed immediately by a 0.<br />

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if 1 is equal to b here, then one possibility that regex gives me is 1* which can be an empty string and it is not followed immediately by a 0.


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ozo can you please explain that a bit<br />

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<br />
on the picture below, the start state is when given an input b, what if the input at the start state is a? It doesn't covers that..<br />
<a href="https://filedb.experts-exchange.com/incoming/2008/10_w40/64545/dfa.png" target="_blank" class="file-inline" title="dfa (8 KB)"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path d="M67.508 468.467c-58.005-58.013-58.016-151.92 0-209.943l225.011-225.04c44.643-44.645 117.279-44.645 161.92 0 44.743 44.749 44.753 117.186 0 161.944l-189.465 189.49c-31.41 31.413-82.518 31.412-113.926.001-31.479-31.482-31.49-82.453 0-113.944L311.51 110.491c4.687-4.687 12.286-4.687 16.972 0l16.967 16.971c4.685 4.686 4.685 12.283 0 16.969L184.983 304.917c-12.724 12.724-12.73 33.328 0 46.058 12.696 12.697 33.356 12.699 46.054-.001l189.465-189.489c25.987-25.989 25.994-68.06.001-94.056-25.931-25.934-68.119-25.932-94.049 0l-225.01 225.039c-39.249 39.252-39.258 102.795-.001 142.057 39.285 39.29 102.885 39.287 142.162-.028A739446.174 739446.174 0 0 1 439.497 238.49c4.686-4.687 12.282-4.684 16.969.004l16.967 16.971c4.685 4.686 4.689 12.279.004 16.965a755654.128 755654.128 0 0 0-195.881 195.996c-58.034 58.092-152.004 58.093-210.048.041z"/></svg>dfa.png</a>
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on the picture below, the start state is when given an input b, what if the input at the start state is a? It doesn't covers that..
dfa.png [https://filedb.experts-exchange.com/incoming/2008/10_w40/64545/dfa.png]

dfa.png

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<div class="content wysiwyg-content">
How do you draw this in a DFA?<br />
<br />
w | each 1 in w is immediately preceded and immediately followed by a 0
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How do you draw this in a DFA?

w | each 1 in w is immediately preceded and immediately followed by a 0

regular expression to DFA

A regular expression ("regex") is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. Regular expression processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK. Many programming languages provide regular expression capabilities, some built-in, for example Perl, JavaScript, Ruby, AWK, and Tcl, and others via a standard library, for example .NET languages, Java, Python and C++ (since C++11). Most other languages offer regular expressions via a library.