[r-t] Bobs only Erin Triples (was: Composition search)

Ian Broster ian at broster.co.uk
Wed Nov 25 14:03:24 UTC 2015

>> For example, if your path from root to node is ppppppb (because you have
>> already found that ppppppp is false (or actually, comes round and makes
>> any longer touch containing it false - awkward corner case!) then you do
>> not need to try (ever) the sequence ppppppp in your search space. You do
>> this by using the path ppppppb to prune direct the next recursive call.
>> Sorry that's not explained very well! It was years ago I last coded
>> something like that.
> Actually, that's perfectly clear. The rotations point is interesting as  
> well, although checking if one path is a rotation of another might be  
> fairly expensive, especially as the paths get longer.

The point is that this algorithm automatically prunes all rotations "by  
construction" - there is no checking to do.

Ian Broster

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