What is a practical solution to the Travelling Salesman problem, using Google Maps / geolocation / route finding?
I don't need the best solution, within 5% would be fine.
For example, I have 20 locations in the UK to visit, in any order. This may need to scale to hundreds of locations.
What sort of algorithm can I use, given that I can lookup distances (but don't want to lookup hundreds of distances)?
I you are looking for a polynomial approximation for the Euclidean TSP, several algorithms have been suggested. Have a look here.
There is this TSP project implemented in JS http://code.google.com/p/google-maps-tsp-solver/
You can see live demo here http://gebweb.net/optimap/
Google does have a parameter on their directions API which will optimize the route as a travelling salesman problem:
- API Documentation: Using Waypoints in Routes
- Introduction and demo blog post
From the documentation (the key part is &waypoints=optimize:true|...):
The following example calculates a road trip route from Adelaide, South Australia to each of South Australia's main wine regions using route optimization.
http://maps.googleapis.com/maps/api/directions/json?origin=Adelaide,SA &destination=Adelaide,SA &waypoints=optimize:true|Barossa+Valley,SA|Clare,SA|Connawarra,SA|McLaren+Vale,SA &sensor=falseInspection of the calculated route will indicate that the route is calculated using the following waypoint order:
"waypoint_order": [ 1, 0, 2, 3 ]
For a one-off it's probably easier to use OptiMap as recommended by @Kunukn
you can use long lat to estimated roughly how far apart the locations are, then make a few lookups for those that are nearby each other.
a simpler alternative is to separate your map into 3 x 3 sections. Only look up routes for locations in adjacent sections.
these techniques aren't 100% accurate though.
And even if you look up all the paths, you should end up with no more than 190 lookups.
来源：https://stackoverflow.com/questions/7736674/what-is-a-practical-solution-to-the-travelling-salesman-prblem-using-google-map