title: One-way flight trip problem
body: <p>You are going on a one-way indirect flight trip that includes <strike>billions</strike> <em>an unknown very large number</em> of transfers. </p>
  
  <ul>
  <li>You are not stopping twice in the same airport. </li>
  <li>You have 1 ticket for each part of your trip. </li>
  <li>Each ticket contains <strong>src</strong> and <strong>dst</strong> airport. </li>
  <li>All the tickets you have are randomly sorted. </li>
  <li>You forgot the original departure airport (very first src) and your destination (last dst).</li>
  </ul>
  
  <p>Design an algorithm to reconstruct your trip with minimum big-<strong>O</strong> complexity.</p>
  
  <hr>
  
  <p>Attempting to solve this problem I have started to use a <a href="http://en.wikipedia.org/wiki/Symmetric_difference" rel="noreferrer">symmetric difference</a> of two sets, Srcs and Dsts:</p>
  
  <p>1)Sort all src keys in array Srcs <br>
  2)Sort all dst keys in array Dsts <br>
  3)Create an union set of both arrays to find non-duplicates - they are your first src and last dst <br>
  4)Now, having the starting point, traverse both arrays using the binary search.</p>
  
  <p>But I suppose there must be another more effective method.</p>