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: "improving christofides algorithm for the s t path tsp"
  Abstract: We present a deterministic (1+sqrt(5))/2-approximation algorithm for the s-t path TSP for an arbitrary metric. Given a symmetric metric cost on n vertices including two prespecified endpoints, the problem is to find a shortest Hamiltonian path between the two endpoints; Hoogeveen showed that the natural variant of Christofides' algorithm is a 5/3-approximation algorithm for this problem, and this asymptotically tight bound in fact has been the best approximation ratio known until now. We modify this algorithm so that it chooses the initial spanning tree based on an optimal solution to the Held-Karp relaxation rather than a minimum spanning tree; we prove this simple but crucial modification leads to an improved approximation ratio, surpassing the 20-year-old barrier set by the natural Christofides' algorithm variant. Our algorithm also proves an upper bound of (1+sqrt(5))/2 on the integrality gap of the path-variant Held-Karp relaxation. The techniques devised in this paper can be applied to other optimization problems as well: these applications include improved approximation algorithms and improved LP integrality gap upper bounds for the prize-collecting s-t path problem and the unit-weight graphical metric s-t path TSP.

Connected through hyperedge HE-1 (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"
    - "approximating minimum cost connected t joins"
    - "13 9 approximation for graphic tsp"

Connected through hyperedge HE-2 (induced by source paper "a constant factor approximation for directed latency in quasi polynomial time"):
  with members:
    - "the asymmetric traveling salesman path lp has constant integrality ratio"
    - "a constant factor approximation algorithm for the asymmetric traveling salesman problem"
    - "compact provably good lps for orienteering and regret bounded vehicle routing"
    - "an improved integrality gap for asymmetric tsp paths"
    - "approximation algorithms for regret bounded vehicle routing and applications to distance constrained vehicle routing"
    - "asymmetric traveling salesman path and directed latency problems"

Connected through hyperedge HE-3 (induced by source paper "beating the integrality ratio for s t tours in graphs"):
  with members:
    - "a 1 5 approximation for path tsp"
    - "an improved upper bound on the integrality ratio for the s t path tsp"
    - "a constant factor approximation algorithm for the asymmetric traveling salesman problem"
    - "approaching frac 3 2 for the s t path tsp"
    - "approximation hardness of graphic tsp on cubic graphs"

Connected through hyperedge HE-4 (induced by source paper "an improved upper bound on the integrality ratio for the s t path tsp"):
  with members:
    - "a 1 5 approximation for path tsp"
    - "layers and matroids for the traveling salesman s paths"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"
    - "eight fifth approximation for the path tsp"

Connected through hyperedge HE-5 (induced by source paper "a constant factor approximation algorithm for the asymmetric traveling salesman problem"):
  with members:
    - "the asymmetric traveling salesman path lp has constant integrality ratio"
    - "constant factor approximation for atsp with two edge weights"
    - "approximating atsp by relaxing connectivity"
    - "effective resistance reducing flows spectrally thin trees and asymmetric tsp"
    - "new inapproximability bounds for tsp"
    - "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"
    - "13 9 approximation for graphic tsp"
    - "the asymmetric traveling salesman problem on graphs with bounded genus"

Connected through hyperedge HE-6 (induced by source paper "approaching frac 3 2 for the s t path tsp"):
  with members:
    - "a 1 5 approximation for path tsp"
    - "an improved upper bound on the integrality ratio for the s t path tsp"
    - "layers and matroids for the traveling salesman s paths"
    - "better s t tours by gao trees"
    - "reassembling trees for the traveling salesman"

Connected through hyperedge HE-7 (induced by source paper "layers and matroids for the traveling salesman s paths"):
  with members:
    - "better s t tours by gao trees"

Connected through hyperedge HE-8 (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"
    - "approximating minimum cost connected t joins"
    - "approximating graphic tsp by matchings"
    - "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)