title: Find the shortest path in a graph visiting all nodes
body: <p>I have a weighted and undirected graph <code>G</code> with <code>n</code> vertices. Two of these vertices are <code>X</code> and <code>Y</code>. <br>I need to find the shortest path that starts at <code>X</code>, ends at <code>Y</code> and passes through all the vertices of G (in any order).<br>
  How I can do this? </p>
  
  <p>This is not the Travelling Salesman Problemm: I don't need to visit each vertex just once and I don't want to return to the first vertex.</p>