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: "a note on johnson minkoff and phillips algorithm for the prize collecting steiner tree problem"
  Abstract: The primal-dual scheme has been used to provide approximation algorithms for many problems. Goemans and Williamson gave a (2− 1 n 1 )-approximation for the Prize-Collecting Steiner Tree Problem that runs in O(n 3 logn) time. Johnson, Minkoff and Phillips proposed a faster implementation of Goemans and Williamson’s algorithm. We give a proof that the approximation ratio of this implementation is exactly 2 (in the worst case).

Connected through hyperedge HE-1 (induced by source paper "a 2 approximation for the k prize collecting steiner tree problem"):
  with members:
    - "a 4 approximation algorithm for k prize collecting steiner tree problems"

Connected through hyperedge HE-2 (induced by source paper "the fast heuristic algorithms and post processing techniques to design large and low cost communication networks"):
  with members:
    - "duty cycle aware minimum energy multicasting in wireless sensor networks"

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)