Tomorrow I'll have the "midterm" of Combinatorial Optimization. It's not exactly a midterm, since it is considerably skewed towards the end of the semester and I'll have 3 other tests until the course is finished, but I guess that having this many tests is actually better than having only two.

I'm terribly tired, sad (I'm not emotionally very well) and without much motivation to study for my test. I have a reasonbly good grasp of the theory, but some details of the subject didn't "sink in" up till now and I'm not very much optimistic regarding what I can do until tomorrow. In particular, finding negative cycles efficiently (i.e., in polynomial time) is still a mystery for me. I have some intuition of why the O(nm) algorithm works, but I have still to sit down and write a complete, detailed a proof. I wish I had time.