Steven Taschuk wrote: ... > trade-off as being between, say, an algorithm which runs in O(n) > time but needs O(n^2) memory to do it, and an alternative which I don't think there can be any such algorithm -- in O(n) time, the algoritm cannot USE more than O(n) memory, so how could it NEED it...? The reverse, sure, but not this way, I think. Alex