I thought that the bipartite graph algorithm question was the best so far. It was a question that, in addition to remembering what a bipartite graph is, required a little bit of thinking instead of just rote memorization (if you know what a bipartite graph is you can come up with the algorithm on your own -- no need to memorize that). Question #2 in this set is also pretty good.
Remembering the relation of a bipartite graph to graph coloring helped me coming up with an algorithm fairly quickly. Although that might in fact require a little familiarity with graphs and the associated terms. I guess most of my former fellow students who didn't hear a graph theory lecture won't really remember that.
