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: "a 9 7 approximation algorithm for graphic tsp in cubic bipartite graphs"
  Abstract: We prove new results for approximating Graphic TSP. Specifically, we provide a polynomial-time \frac{9}{7}-approximation algorithm for cubic bipartite graphs and a (\frac{9}{7}+\frac{1}{21(k-2)})-approximation algorithm for k-regular bipartite graphs, both of which are improved approximation factors compared to previous results. Our approach involves finding a cycle cover with relatively few cycles, which we are able to do by leveraging the fact that all cycles in bipartite graphs are of even length along with our knowledge of the structure of cubic graphs.

Connected through hyperedge HE-1 (induced by source paper "improved approximations for cubic and cubic bipartite tsp"):
  with members:
    - "cubic tsp a 1 3 approximation"
    - "tsp tours in cubic graphs beyond 4 3"
    - "approximating graphic tsp by matchings"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-2 (induced by source paper "cubic tsp a 1 3 approximation"):
  with members:
    - "graphic tsp in cubic graphs"
    - "the traveling salesman problem on cubic and subcubic graphs"

Connected through hyperedge HE-3 (induced by source paper "tsp tours in cubic graphs beyond 4 3"):
  with members:
    - "eight fifth approximation for the path tsp"
    - "approximation hardness of graphic tsp on cubic graphs"
    - "improved inapproximability for tsp"
    - "on the integrality gap of the subtour lp for the 1 2 tsp"
    - "improving christofides algorithm for the s t path tsp"
    - "approximating graphic tsp by matchings"
    - "a 4 3 approximation for tsp on cubic 3 edge connected graphs"
    - "a proof of the boyd carr conjecture"

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.DS(Data Structures and Algorithms)