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: "simple ptas s for families of graphs excluding a minor"
  Abstract: We show that very simple algorithms based on local search are polynomial-time approximation schemes for Maximum Independent Set, Minimum Vertex Cover ?and Minimum Dominating Set, when the input graphs have a fixed forbidden minor.

Connected through hyperedge HE-1 (induced by source paper "ptas for steiner tree on map graphs"):
  with members:
    - "polynomial time approximation scheme for minimum k cut in planar and minor free graphs"
    - "local search yields approximation schemes for k means and k median in euclidean and minor free metrics"
    - "an efficient polynomial time approximation scheme for steiner forest in planar graphs"
    - "approximate tree decompositions of planar graphs in linear time"
    - "approximation schemes for steiner forest on planar graphs and graphs of bounded treewidth"

Connected through hyperedge HE-2 (induced by source paper "baker game and polynomial time approximation schemes"):
  with members:
    - "thin graph classes and polynomial time approximation schemes"
    - "approximation algorithms for polynomial expansion and low density graphs"
    - "deciding first order properties of nowhere dense graphs"
    - "bidimensionality and eptas"

Connected through hyperedge HE-3 (induced by source paper "local search is a ptas for feedback vertex set in minor free graphs"):
  with members:
    - "local search yields approximation schemes for k means and k median in euclidean and minor free metrics"
    - "approximation algorithms for polynomial expansion and low density graphs"
    - "solving the undirected feedback vertex set problem by local search"
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "separator theorems for minor free and shallow minor free graphs with applications"
    - "bidimensionality and eptas"
    - "eigenvalue bounds spectral partitioning and metrical deformations via flows"

Connected through hyperedge HE-4 (induced by source paper "a local search algorithm for steiner forest"):
  with members:
    - "local search yields a ptas for k means in doubling metrics"
    - "online steiner tree with deletions"
    - "local search based approximation algorithms for mobile facility location problems"

Connected through hyperedge HE-5 (induced by source paper "thin graph classes and polynomial time approximation schemes"):
  with members:
    - "approximation algorithms for polynomial expansion and low density graphs"
    - "bidimensionality and eptas"

Connected through hyperedge HE-6 (induced by source paper "approximation algorithms for polynomial expansion and low density graphs"):
  with members:
    - "approximation algorithms for low density graphs"
    - "net and prune a linear time algorithm for euclidean distance problems"
    - "qptas for geometric set cover problems via optimal separators"
    - "quasi polynomial time approximation scheme for sparse subsets of polygons"
    - "deciding first order properties of nowhere dense graphs"
    - "approximation schemes for maximum weight independent set of rectangles"
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "a simple proof of the existence of a planar separator"

Connected through hyperedge HE-7 (induced by source paper "approximation algorithms for low density graphs"):
  with members:
    - "net and prune a linear time algorithm for euclidean distance problems"
    - "qptas for geometric set cover problems via optimal separators"
    - "quasi polynomial time approximation scheme for sparse subsets of polygons"
    - "approximation schemes for maximum weight independent set of rectangles"
    - "approximation algorithms for maximum independent set of pseudo disks"
    - "a simple proof of the existence of a planar separator"
    - "being fat and friendly is not enough"
    - "improved approximation algorithms for geometric set cover"

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)