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: "directed spanners via flow based linear programs"
  Abstract: We examine directed spanners through flow-based linear programming relaxations. We design an $\~O(n^{2/3})$-approximation algorithm for the directed $k$-spanner problem that works for all $k\geq 1$, which is the first sublinear approximation for arbitrary edge-lengths. Even in the more restricted setting of unit edge-lengths, our algorithm improves over the previous $\~O(n^{1-1/k})$ approximation of Bhattacharyya et al. when $k\ge 4$. For the special case of $k=3$ we design a different algorithm achieving an $\~O(\sqrt{n})$-approximation, improving the previous $\~O(n^{2/3})$. Both of our algorithms easily extend to the fault-tolerant setting, which has recently attracted attention but not from an approximation viewpoint. We also prove a nearly matching integrality gap of $\Omega(n^{\frac13 - \epsilon})$ for any constant $\epsilon > 0$. #R##N#A virtue of all our algorithms is that they are relatively simple. Technically, we introduce a new yet natural flow-based relaxation, and show how to approximately solve it even when its size is not polynomial. The main challenge is to design a rounding scheme that "coordinates" the choices of flow-paths between the many demand pairs while using few edges overall. We achieve this, roughly speaking, by randomization at the level of vertices.

Connected through hyperedge HE-1 (induced by source paper "lasserre integrality gaps for graph spanners and related problems"):
  with members:
    - "characterizing demand graphs for fixed parameter shallow light steiner network"
    - "approximating spanners and directed steiner forest upper and lower bounds"
    - "parallel metric tree embedding based on an algebraic view on moore bellman ford"
    - "everywhere sparse spanners via dense subgraphs"
    - "label cover instances with large girth and the hardness of approximating basic k spanner"
    - "rounding semidefinite programming hierarchies via global correlation"
    - "fault tolerant spanners better and simpler"
    - "directed steiner tree and the lasserre hierarchy"

Connected through hyperedge HE-2 (induced by source paper "the norms of graph spanners"):
  with members:
    - "sherali adams integrality gaps matching the log density threshold"
    - "the greedy spanner is existentially optimal"
    - "minimizing the union tight approximations for small set bipartite vertex expansion"
    - "label cover instances with large girth and the hardness of approximating basic k spanner"
    - "fault tolerant spanners better and simpler"
    - "transitive closure spanners"

Connected through hyperedge HE-3 (induced by source paper "approximation algorithms and an integer program for multi level graph spanners"):
  with members:
    - "multi level steiner trees"
    - "linear size distance preservers"
    - "on pairwise spanners"
    - "transitive closure spanners"

Connected through hyperedge HE-4 (induced by source paper "roundtrip spanners with 2k 1 stretch"):
  with members:
    - "improved girth approximation and roundtrip spanners"
    - "approximating cycles in directed graphs fast algorithms for girth and roundtrip spanners"

Connected through hyperedge HE-5 (induced by source paper "distributed spanner approximation"):
  with members:
    - "distributed approximation of minimum k edge connected spanning subgraphs"
    - "improved deterministic distributed construction of spanners"
    - "distributed property testing for subgraph freeness revisited"
    - "quadratic and near quadratic lower bounds for the congest model"
    - "on derandomizing local distributed algorithms"
    - "distributed distance bounded network design through distributed convex programming"
    - "near linear lower bounds for distributed distance computations even in sparse networks"
    - "efficient algorithms for constructing very sparse spanners and emulators"

Connected through hyperedge HE-6 (induced by source paper "a fast network decomposition algorithm and its applications to constant time distributed computation"):
  with members:
    - "distributed symmetry breaking in hypergraphs"
    - "distributed approximation algorithms for weighted shortest paths"
    - "the locality of distributed symmetry breaking"
    - "super fast 3 ruling sets"
    - "on the locality of some np complete problems"
    - "deterministic distributed vertex coloring in polylogarithmic time"
    - "improved approximation for the directed spanner problem"

Connected through hyperedge HE-7 (induced by source paper "network design problems with bounded distances via shallow light steiner trees"):
  with members:
    - "transitive closure spanners"

Connected through hyperedge HE-8 (induced by source paper "label cover instances with large girth and the hardness of approximating basic k spanner"):
  with members:
    - "parameters of two prover one round game and the hardness of connectivity problems"
    - "fault tolerant spanners better and simpler"
    - "improved approximation for the directed spanner problem"
    - "transitive closure spanners"

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)