title: How does route finding software work?
body: <p>I'm asking at a pretty high, language independent, level.</p>
  
  <p>How does route finding (as found in Google Maps 'Get directions' or a GPS) work? I can't believe it tries every conceivable route and chooses the shortest/fastest etc. There must be some logical way of finding the best route given a start and end point.</p>
  
  <p>Any sort of explanation would be great.</p>