Space complexity of alg P

[Thore Husfeldt]

As it stands, algorithm P requires O(|X|) space. This can be fixed either by noting that P4 can be interleaved into P3, or rewriting P.

[Isak Lyckberg]

I have thought about it, and I suggest stating that the two steps can be interleaved, and making a corollary of it, to keep the algorithm clear. Is that an acceptable use of the notion of a corollary?

[Isak Lyckberg]

Should be resolved in new commit.