The universe may include random, or changing elements, we truly don’t know yet. At any given moment, Maxwell’s Demon might be able to describe a complete wavefunction which amounts to “the observable universe,” but we don’t really know if the evolution of the wavefunction would be deterministic.

Mind you, the universe could be infinite as well, which would throw a bit of a wrench into it. All of which is to say that there may not be an algorithm the universe follows, even in principle.