在 Scheme/Racket 中实现 A* 搜索算法

Question

I am looking forward to implement the A* search algorithm but I dont know where I should really start. I came up with a way to represent my graph like so:

(
'("city1" (x y (("neighbour1" edgeWeight1)("neighbour2" edgeWeight2))))
...
)

I created an openlist and a closedlist, but from this point on I don't really know what to do. Any ideas?

Answer 1

The first thing you should do when trying to implement an algorithm is implementing the abstractions the algorithm uses.

The A* search algorithm uses two abstractions. The first abstraction is that of a graph. You should come up with some definition of a graph and implement functions to do "graph-y things" that A* requires (eg getting the neighbours of a given node, finding all nodes in a graph, etc.).

The second abstraction which A* search uses is that of a priority queue, which is used for the "open set". You will need to come up a Scheme definition for the "open set" and write Scheme functions to do the things which must be done (ie find and remove the node with the lowest cost).

Once you do those things, you should find the algorithm to be fairly straightforward.