title: Regular expressions and automata
body: <p>I'm studying Regular Expressions by reading Aho's book. I don't understand two of the statements in the book:</p>
  
  <p><strong>Question A:</strong></p>
  
  <pre><code>1(0+1)*1 + 1 : denotes the set of all strings beginning and ending with a 1.
  </code></pre>
  
  <p>My question why is <code>+1</code> added at end of the regular expression? Shouldn't <code>1(0+1)*1</code> be sufficient?</p>
  
  <hr>
  
  <p>I'm also having trouble with the following:</p>
  
  <p><strong>Question B:</strong></p>
  
  <blockquote>
    <p>The set of strings containing only 0's and 1's that have atmost one 1  as below</p>
  </blockquote>
  
  <pre><code>    0*+0*10* 
  </code></pre>
  
  <p>Can you explain how the solution <code>0*+0*10*</code> is arrived at, step by step?</p>