something like this?
create index on :Room(id)
// find the two rooms and all paths between them
match path = (:Room {id:1})-[:DOOR*0..]->(:Room {id:10})
// take path, keys and doors as collections
with path, extract(room IN nodes(path) | coalesce(room.key,-1)) as keys,
rels(path) as doors
// condition for all doors
// either no lock or the lock-number is in the collection of keys collected so
far
where all(idx in range(0,size(doors)-1) WHERE NOT doors[idx].lock OR
doors[idx].lock IN keys[0..idx])
// return the path(s)
return path;
Perhaps you can provide a sample graph, then this could become a fun graphgist
(graphgist.neo4j.com <http://graphgist.neo4j.com/>) and a really good blog
post. WDYT ?
Cheers, Michael
> Am 26.08.2015 um 14:20 schrieb James Newton <[email protected]>:
>
> I do not have much experience with Neo4j. For the project that I am just
> starting I am hoping that Neo4j will provide a good solution to the following
> problem.
>
> Imagine a maze with rooms (nodes) and doors (relationships) between the
> rooms. The doors to some rooms are locked and their keys are held in other
> rooms (as properties).
>
> In the attached image, you can reach room D by following the path A->B->C->A,
> picking up the key for room D in room B. However it is not possible to reach
> room F, since the key to room F is in room E, and the key to room E is in
> room D, and there is no way back from room D to room A, so room E is
> inaccessible (Creating a new door from room D to room C would make this
> possible).
>
> I understand how I can use Neo4j to trace a path from room to room, but is it
> possible to create queries which take into account the keys that can be
> picked up on the way? For example:
> Is it possible to get from room X to room Y?
> What are all the paths that lead from room A to room Z?
> I'm in room N with these keys. Have I come to a dead end?
> What keys do I need to get from the Library to the Conservatory?
> I can imagine ways of doing this that make multiple queries to the database,
> with each new query being dependent on the result of the previous ones, but
> this is likely to be laborious.
>
> I can also imagine a single Cypher query that creates a temporary node, adds
> keys to this node as it traverses the graph, and checks at each
> door-relationship whether it has the appropriate key to continue in that
> direction. However, I don't know enough about Cypher to know whether this can
> be done.
>
> I'm more than happy to solve this problem myself, if you can confirm that
> Neo4j can do this.
>
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