title: Codeigniter Routing not equal to pattern
body: <p>I am working on a codeigniter app and am having some trouble wrapping my head around a routing issue. Basically I would like all routes to map to an specific controller action by default, but I would also like to able to specify an array of routes (or ideally initial url segments) which shouldn't follow this pattern. </p>
  
  <p>By way of example:</p>
  
  <p>If I enter domain.com/username it maps to domain.com/controller/method/show/username</p>
  
  <p>If I enter domain.com/account it maps to domain.com/account</p>
  
  <p>Any help very gratefully received!</p>
  
  <p>James</p>