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: "treewidth reduction for constrained separation and bipartization problems"
  Abstract: We present a method for reducing the treewidth of a graph while preserving all the minimal $s-t$ separators. This technique turns out to be very useful for establishing the fixed-parameter tractability of constrained separation and bipartization problems. To demonstrate the power of this technique, we prove the fixed-parameter tractability of a number of well-known separation and bipartization problems with various additional restrictions (e.g., the vertices being removed from the graph form an independent set). These results answer a number of open questions in the area of parameterized complexity.

Connected through hyperedge HE-1 (induced by source paper "on the parameterized complexity of computing balanced partitions in graphs"):
  with members:
    - "expanding the expressive power of monadic second order logic on restricted graph classes"
    - "minimum bisection is fixed parameter tractable"
    - "kernelization lower bounds by cross composition"
    - "fast balanced partitioning is hard even on grids and trees"
    - "finding small separators in linear time via treewidth reduction"
    - "cross composition a new technique for kernelization lower bounds"

Connected through hyperedge HE-2 (induced by source paper "parameterized complexity dichotomy for r ell vertex deletion"):
  with members:
    - "faster parameterized algorithms using linear programming"
    - "finding small separators in linear time via treewidth reduction"
    - "problems parameterized by treewidth tractable in single exponential time a logical approach"
    - "compression via matroids a randomized polynomial kernel for odd cycle transversal"

Connected through hyperedge HE-3 (induced by source paper "linear time parameterized algorithms via skew symmetric multicuts"):
  with members:
    - "half integrality lp branching and fpt algorithms"
    - "linear time fpt algorithms via network flow"
    - "faster parameterized algorithms using linear programming"
    - "representative sets and irrelevant vertices new tools for kernelization"
    - "backdoors to satisfaction"
    - "finding small separators in linear time via treewidth reduction"
    - "compression via matroids a randomized polynomial kernel for odd cycle transversal"
    - "on multiway cut parameterized above lower bounds"

Connected through hyperedge HE-4 (induced by source paper "finding small separators in linear time via treewidth reduction"):
  with members:
    - "contracting graphs to paths and trees"
    - "obtaining a bipartite graph by contracting few edges"
    - "on multiway cut parameterized above lower bounds"
    - "multicut is fpt"
    - "fixed parameter tractability of multicut parameterized by the size of the cutset"
    - "almost 2 sat is fixed parameter tractable"
    - "minimum cost homomorphisms to reflexive digraphs"
    - "minimum cost homomorphisms to proper interval graphs and bigraphs"

Connected through hyperedge HE-5 (induced by source paper "on polynomial kernels for structural parameterizations of odd cycle transversal"):
  with members:
    - "preprocessing for treewidth a combinatorial analysis through kernelization"
    - "compression via matroids a randomized polynomial kernel for odd cycle transversal"
    - "hitting forbidden minors approximation and kernelization"
    - "multicut is fpt"
    - "fixed parameter tractability of multicut parameterized by the size of the cutset"
    - "vertex cover kernelization revisited upper and lower bounds for a refined parameter"
    - "cross composition a new technique for kernelization lower bounds"

Connected through hyperedge HE-6 (induced by source paper "multicut is fpt"):
  with members:
    - "fixed parameter tractability of multicut parameterized by the size of the cutset"
    - "a polynomial kernel for multicut in trees"

Connected through hyperedge HE-7 (induced by source paper "computing multiway cut within the given excess over the largest minimum isolating cut"):
  with members:
    - "all ternary permutation constraint satisfaction problems parameterized above average have kernels with quadratic numbers of variables"
    - "almost 2 sat is fixed parameter tractable"

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)