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: "not so easy problems for tree decomposable graphs"
  Abstract: We consider combinatorial problems that can be solved in polynomial time for graphs of bounded treewidth but where the order of the polynomial that bounds the running time is expected to depend on the treewidth bound. First we review some recent results for problems regarding list and equitable colorings, general factors, and generalized satisfiability. Second we establish a new hardness result for the problem of minimizing the maximum weighted outdegree for orientations of edge-weighted graphs of bounded treewidth.

Connected through hyperedge HE-1 (induced by source paper "parameterized orientable deletion"):
  with members:
    - "on the configuration lp for scheduling on unrelated machines"
    - "known algorithms on graphs of bounded treewidth are probably optimal"
    - "on allocating goods to maximize fairness"

Connected through hyperedge HE-2 (induced by source paper "weighted proper orientations of trees and graphs of bounded treewidth"):
  with members:
    - "ruling out fpt algorithms for weighted coloring on forests"
    - "the complexity of the proper orientation number"

Connected through hyperedge HE-3 (induced by source paper "complexity and approximability of parameterized max csps"):
  with members:
    - "solving maxsat and sat on structured cnf formulas"
    - "tractable answer set programming with weight constraints bounded treewidth is not enough"
    - "guarantees and limits of preprocessing in constraint satisfaction and reasoning"
    - "model counting for formulas of bounded clique width"
    - "a characterization of approximation resistance for even k partite csps"
    - "satisfiability of acyclic and almost acyclic cnf formulas"
    - "majority is stablest discrete and sos"
    - "backdoors to acyclic sat"

Connected through hyperedge HE-4 (induced by source paper "structural parameters for scheduling with assignment restrictions"):
  with members:
    - "scheduling meets n fold integer programming"

Connected through hyperedge HE-5 (induced by source paper "complexity of secure sets"):
  with members:
    - "optimizing tree decompositions in mso"
    - "the parameterized complexity of reasoning problems beyond np"

Connected through hyperedge HE-6 (induced by source paper "matchings with lower quotas algorithms and complexity"):
  with members:
    - "profile based optimal matchings in the student project allocation problem"

Connected through hyperedge HE-7 (induced by source paper "tractable answer set programming with weight constraints bounded treewidth is not enough"):
  with members:
    - "stable models and an alternative logic programming paradigm"

Connected through hyperedge HE-8 (induced by source paper "parameterized approximation schemes using graph widths"):
  with members:
    - "approximating the maxcover problem with bounded frequencies in fpt time"
    - "augmenting graphs to minimize the diameter"
    - "parameterized in approximability of subset problems"
    - "the parameterised complexity of list problems on graphs of bounded treewidth"
    - "approximation schemes for steiner forest on planar graphs and graphs of bounded treewidth"

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)