human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "optimal constructions of hybrid algorithms"
  Abstract: We study on-line strategies for solving problems with hybrid algorithms. There is a problem Q and w basic algorithms for solving Q. For some lambda <= w, we have a computer with lambda disjoint memory areas, each of which can be used to run a basic algorithm and store its intermediate results. In the worst case, only one basic algorithm can solve Q in finite time, and all the other basic algorithms run forever without solving Q. To solve Q with a hybrid algorithm constructed from the basic algorithms, we run a basic algorithm for some time, then switch to another, and continue this process until Q is solved. The goal is to solve Q in the least amount of time. Using competitive ratios to measure the efficiency of a hybrid algorithm, we construct an optimal deterministic hybrid algorithm and an efficient randomized hybrid algorithm. This resolves an open question on searching with multiple robots posed by Baeza-Yates, Culberson and Rawlins. We also prove that our randomized algorithm is optimal for lambda = 1, settling a conjecture of Kao, Reif and Tate.

Connected through hyperedge HE-1 (induced by source paper "lower bounds for searching robots some faulty"):
  with members:
    - "search on a line by byzantine robots"
    - "revisiting the problem of searching on a line"
    - "collaborative search on the plane without communication"
    - "online searching with turn cost"

Connected through hyperedge HE-2 (induced by source paper "optimal strategies for weighted ray search"):
  with members:
    - "further connections between contract scheduling and ray searching problems"
    - "online searching with turn cost"
    - "the k server dual and loose competitiveness for paging"

Connected through hyperedge HE-3 (induced by source paper "search and fetch with 2 robots on a disk wireless and face to face communication models"):
  with members:
    - "fast two robot disk evacuation with wireless communication"
    - "evacuating robots from a disk using face to face communication"
    - "evacuation of rectilinear polygons"
    - "online searching with turn cost"

Connected through hyperedge HE-4 (induced by source paper "further connections between contract scheduling and ray searching problems"):
  with members:
    - "online searching with turn cost"

Connected through hyperedge HE-5 (induced by source paper "new techniques for algorithm portfolio design"):
  with members:
    - "algorithm portfolio design theory vs practice"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.DM(Discrete Mathematics)