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: "approximating minimum cost connected t joins"
  Abstract: We design and analyse approximation algorithms for the minimum-cost connected T-join problem: given an undirected graph G = (V;E) with nonnegative costs on the edges, and a subset of nodes T, find (if it exists) a spanning connected subgraph H of minimum cost such that every node in T has odd degree and every node not in T has even degree; H may have multiple copies of any edge of G. Two well-known special cases are the TSP (|T| = 0) and the s-t path TSP (|T| = 2). Recently, An, Kleinberg, and Shmoys [STOC 2012] improved on the long-standing 5/3-approximation guarantee for the latter problem and presented an algorithm based on LP rounding that achieves an approximation guarantee of (1+sqrt(5))/2 < 1.6181. #R##N#We show that the methods of An et al. extend to the minimum-cost connected T-join problem. They presented a new proof for a 5/3-approximation guarantee for the s-t path TSP; their proof extends easily to the minimum-cost connected T-join problem. Next, we improve on the approximation guarantee of 5/3 by extending their LP-rounding algorithm to get an approximation guarantee of 13/8 = 1.625 for all |T| >= 4. #R##N#Finally, we focus on the prize-collecting version of the problem, and present a primal-dual algorithm that is "Lagrangian multiplier preserving" and that achieves an approximation guarantee 3 - 2/(|T|-1) when |T| >= 4. Our primal-dual algorithm is a generalization of the known primal-dual 2-approximation for the prize-collecting s-t path TSP. Furthermore, we show that our analysis is tight by presenting instances with |T| >= 4 such that the cost of the solution found by the algorithm is exactly 3 - 2/(|T|-1) times the cost of the constructed dual solution.

Connected through hyperedge HE-1 (induced by source paper "constant factor approximation algorithms for parity constrained facility location problems"):
  with members:
    - "a tree structure for dynamic facility location"
    - "on facility location with general lower bounds"
    - "online facility location with deletions"
    - "optimal parameterized algorithms for planar facility location problems using voronoi diagrams"
    - "facility location in evolving metrics"
    - "lp based algorithms for capacitated facility location"
    - "eight fifth approximation for the path tsp"
    - "local search based approximation algorithms for mobile facility location problems"

Connected through hyperedge HE-2 (induced by source paper "reducing path tsp to tsp"):
  with members:
    - "beating the integrality ratio for s t tours in graphs"
    - "a 1 5 approximation for path tsp"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"
    - "new inapproximability bounds for tsp"
    - "improving christofides algorithm for the s t path tsp"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-3 (induced by source paper "the salesman s improved paths 3 2 1 34 integrality gap and approximation ratio"):
  with members:
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "on the metric s t path traveling salesman problem"

Connected through hyperedge HE-4 (induced by source paper "reassembling trees for the traveling salesman"):
  with members:
    - "an experimental evaluation of the best of many christofides algorithm for the traveling salesman problem"
    - "better s t tours by gao trees"
    - "on the metric s t path traveling salesman problem"
    - "eight fifth approximation for the path tsp"
    - "improving christofides algorithm for the s t path tsp"
    - "approximating graphic tsp by matchings"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-5 (induced by source paper "better s t tours by gao trees"):
  with members:
    - "layers and matroids for the traveling salesman s paths"
    - "an experimental evaluation of the best of many christofides algorithm for the traveling salesman problem"
    - "reassembling trees for the traveling salesman"
    - "on the metric s t path traveling salesman problem"
    - "eight fifth approximation for the path tsp"
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-6 (induced by source paper "on the metric s t path traveling salesman problem"):
  with members:
    - "improving christofides algorithm for the s t path tsp"

Connected through hyperedge HE-7 (induced by source paper "eight fifth approximation for the path tsp"):
  with members:
    - "shorter tours by nicer ears 7 5 approximation for graphic tsp 3 2 for the path version and 4 3 for two edge connected subgraphs"
    - "improving christofides algorithm for the s t path tsp"
    - "approximating graphic tsp by matchings"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-8 (induced by source paper "an lp based 3 2 approximation algorithm for the graphic s t path tsp"):
  with members:
    - "shorter tours by nicer ears 7 5 approximation for graphic tsp 3 2 for the path version and 4 3 for two edge connected subgraphs"
    - "approximating graphic tsp by matchings"
    - "lp based approximation algorithms for traveling salesman path problems"
    - "13 9 approximation for graphic tsp"

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)