title: Regular expression to match one or more characters every type?
body: <p>There are 3 types of characters: <code>A-Z</code>, <code>a-z</code> and <code>0-9</code>.</p>
  
  <p>How to write regular expression to match words which have one or more characters in all three types?</p>
  
  <p>For example:</p>
  
  <p>Match: <code>abAcc88, Ua8za8, 88aA</code></p>
  
  <p>No match: <code>abc, 118, aa7, xxZZ, XYZ111</code></p>
  
  <p>This <code>boost::regex re("^[A-Za-z0-9]+$");</code> doesn't work.</p>
  
  <p>Thanks</p>