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Comment by yread | Hacker News Reader

I don't understand all of the code but this bit

    > int valbit = Possibles & (-Possibles); // Lowest 1 bit in Possibles

is pretty neat

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It's a standard trick, e.g. https://stackoverflow.com/questions/12247186/find-the-lowest....

If you like that you may also like https://graphics.stanford.edu/~seander/bithacks.html

(Also "Hackers Delight" if you really can't get enough of it.)

I think there’s an Intel intrinsic for this, but nonetheless neat.

It's the kind of thing that I would expect a compiler to know about and use; when writing code in a high level language you shouldn't have to think too much about what happens on the hardware level.

It's done in Java, Integer.lowestOneBit(int), citing HD 2-1. Java defines ints to be 2-complimentary. I can't recall if it's compiled tzcnt[0], though

[0]: https://www.felixcloutier.com/x86/tzcnt

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