title: Regular Expression for validating numbers with one space and one optional special character
body: <p>Can someone tell me how to validate sequence of numbers with one space and at the end there will be a optional special character say '#' and again followed by some 5 digits.</p>
  
  <p>Example:</p>
  
  <blockquote>
    <p>12345 6587#2584</p>
  </blockquote>
  
  <p>I have tried with </p>
  
  <pre><code>(0(?:\d{0,11}|(?=\d* \d*$)[\d ]{0,12}))
  </code></pre>
  
  <p>but I don't know how to add optional '#' in the end followed by digits.</p>