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 ptas for vertex guarding weakly visible polygons an extended abstract"
  Abstract: In this extended abstract, we first present a PTAS for guarding the vertices of a weakly-visible polygon $P$ from a subset of its vertices, or in other words, a PTAS for computing a minimum dominating set of the visibility graph of the vertices of $P$. We then show how to obtain a PTAS for vertex guarding the entire polygon.

Connected through hyperedge HE-1 (induced by source paper "the parameterized complexity of guarding almost convex polygons"):
  with members:
    - "constant approximation algorithms for guarding simple polygons using vertex guards"
    - "irrational guards are sometimes needed"
    - "an approximation algorithm for the art gallery problem"
    - "engineering art galleries"
    - "approximability of guarding weak visibility polygons"
    - "a new upper bound for the vc dimension of visibility regions"
    - "improved approximation for guarding simple galleries from the perimeter"
    - "unsolved problems in visibility graphs of points segments and polygons"

Connected through hyperedge HE-2 (induced by source paper "a constant factor approximation algorithm for vertex guarding a wv polygon"):
  with members:
    - "constant approximation algorithms for guarding simple polygons using vertex guards"
    - "an approximation algorithm for the art gallery problem"
    - "the continuous 1 5d terrain guarding problem discretization optimal solutions and ptas"
    - "approximability of guarding weak visibility polygons"
    - "improved approximation for guarding simple galleries from the perimeter"

Connected through hyperedge HE-3 (induced by source paper "on conflict free chromatic guarding of simple polygons"):
  with members:
    - "an approximation algorithm for the art gallery problem"
    - "approximability of guarding weak visibility polygons"
    - "improved approximation for guarding simple galleries from the perimeter"

Connected through hyperedge HE-4 (induced by source paper "constant approximation algorithms for guarding simple polygons using vertex guards"):
  with members:
    - "an approximation algorithm for the art gallery problem"
    - "vertex guarding in weak visibility polygons"
    - "improved approximation for guarding simple galleries from the perimeter"

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.CG(Computational Geometry)