bool mapClass::IsPath(int OriginCity, int DestinationCity)
{
   int  NextCity;
   bool Success, Done;

   // mark the current city as visited
   MarkVisited(OriginCity);

   // base case: the destination is reached
   if (OriginCity == DestinationCity)
      return true;

   else  // try a flight to each unvisited city
   {  Done = false;
      GetNextCity(OriginCity, NextCity, Success);

      while (Success && !Done)
      {  Done = IsPath(NextCity, DestinationCity);
         if (!Done)
            GetNextCity(OriginCity, NextCity, Success);
      }  // end while

      return Done;
   }  // end if
}  // end IsPath