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: "happy endings for flip graphs"
  Abstract: We show that the triangulations of a finite point set form a flip graph that can be embedded isometrically into a hypercube, if and only if the point set has no empty convex pentagon. Point sets with no empty pentagon include intersections of lattices with convex sets, points on two lines, and several other infinite families. As a consequence, flip distance in such point sets can be computed efficiently.

Connected through hyperedge HE-1 (induced by source paper "a proof of the orbit conjecture for flipping edge labelled triangulations"):
  with members:
    - "reconfiguring ordered bases of a matroid"
    - "flips in edge labelled pseudo triangulations"
    - "flip distance between triangulations of a simple polygon is np complete"
    - "flip distance between triangulations of a planar point set is apx hard"
    - "computing the flip distance between triangulations"
    - "the complexity of change"
    - "flipping edge labelled triangulations"
    - "flip distance between two triangulations of a point set is np complete"

Connected through hyperedge HE-2 (induced by source paper "flip distance between triangulations of a simple polygon is np complete"):
  with members:
    - "flip distance between triangulations of a planar point set is apx hard"
    - "flip distance is in fpt time o n k cdot c k"
    - "flip distance between two triangulations of a point set is np complete"

Connected through hyperedge HE-3 (induced by source paper "flip distance between triangulations of a planar point set is apx hard"):
  with members:
    - "flip distance between triangulations of a simple polygon is np complete"
    - "flipping edge labelled triangulations"
    - "flip distance between two triangulations of a point set is np complete"
    - "rotation distance is fixed parameter tractable"

Connected through hyperedge HE-4 (induced by source paper "flipping edge labelled triangulations"):
  with members:
    - "arc diagrams flip distances and hamiltonian triangulations"
    - "flip distance between triangulations of a planar point set is apx hard"
    - "a history of flips in combinatorial triangulations"
    - "the complexity of rerouting shortest paths"
    - "the connectivity of boolean satisfiability computational and structural dichotomies"

Connected through hyperedge HE-5 (induced by source paper "practical reduction of edge flip sequences in two dimensional triangulations"):
  with members:
    - "flip distance between triangulations of a simple polygon is np complete"
    - "flip distance between triangulations of a planar point set is apx hard"
    - "making triangulations 4 connected using flips"
    - "flip distance between two triangulations of a point set is np complete"

Connected through hyperedge HE-6 (induced by source paper "flip distance between two triangulations of a point set is np complete"):
  with members:
    - "flip distance between triangulations of a simple polygon is np complete"
    - "flip distance between triangulations of a planar point set is apx hard"
    - "making triangulations 4 connected using flips"
    - "rotation distance is fixed parameter tractable"

Connected through hyperedge HE-7 (induced by source paper "recognizing partial cubes in quadratic time"):
  with members:
    - "optimal angular resolution for face symmetric drawings"
    - "isometric diamond subgraphs"
    - "upright quad drawing of st planar learning spaces"
    - "the lattice dimension of a graph"
    - "algorithms for drawing media"
    - "algorithms for media"

Connected through hyperedge HE-8 (induced by source paper "triangulating the real projective plane"):
  with members:
    - "minimum weight triangulation is np hard"
    - "finding an ordinary conic and an ordinary hyperplane"

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.CG(Computational Geometry)