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: "on approximating tree spanners that are breadth first search trees"
  Abstract: There are known efficient algorithms that approximate the minimum t for which a graph admits a tree t-spanner with ratio O ( log ? n ) . Unless there is an algorithm that decides 3-SAT in quasi-polynomial time, it is impossible to approximate efficiently the minimum t for which a graph admits a tree t-spanner that is a breadth first search tree starting from a given vertex with ratio almost o ( log ? n ) . NP-completeness of diameter at most t + 1 tree t-spanner problem is used.Tree spanners that are BFS trees may not be approximated within log factor.Known upper bound for approximation ratio is almost reached.

Connected through hyperedge HE-1 (induced by source paper "tree spanners of bounded degree graphs"):
  with members:
    - "tree spanners of small diameter"
    - "tree 3 spanners of diameter at most 5"
    - "tree t spanners in outerplanar graphs via supply demand partition"
    - "nearly linear time algorithms for graph partitioning graph sparsification and solving linear systems"

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.CC(Computational Complexity)