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: "the complexity of flood filling games"
  Abstract: We study the complexity of the popular one player combinatorial game known as Flood-It. In this game the player is given an n by n board of tiles where each tile is allocated one of c colours. The goal is to make the colours of all tiles equal via the shortest possible sequence of flooding operations. In the standard version, a flooding operation consists of the player choosing a colour k, which then changes the colour of all the tiles in the monochromatic region connected to the top left tile to k. After this operation has been performed, neighbouring regions which are already of the chosen colour k will then also become connected, thereby extending the monochromatic region of the board. We show that finding the minimum number of flooding operations is NP-hard for c>=3 and that this even holds when the player can perform flooding operations from any position on the board. However, we show that this "free" variant is in P for c=2. We also prove that for an unbounded number of colours, Flood-It remains NP-hard for boards of height at least 3, but is in P for boards of height 2. Next we show how a c-1 approximation and a randomised 2c/3 approximation algorithm can be derived, and that no polynomial time constant factor, independent of c, approximation algorithm exists unless P=NP. We then investigate how many moves are required for the "most demanding" n by n boards (those requiring the most moves) and show that the number grows as fast as Theta(n*c^0.5). Finally, we consider boards where the colours of the tiles are chosen at random and show that for c>=2, the number of moves required to flood the whole board is Omega(n) with high probability.

Connected through hyperedge HE-1 (induced by source paper "spanning trees and the complexity of flood filling games"):
  with members:
    - "the complexity of free flood it on 2ixn boards"
    - "the complexity of flood filling games on graphs"
    - "an algorithmic analysis of the honey bee game"

Connected through hyperedge HE-2 (induced by source paper "the complexity of free flood it on 2ixn boards"):
  with members:
    - "spanning trees and the complexity of flood filling games"
    - "the complexity of flood filling games on graphs"
    - "an algorithmic analysis of the honey bee game"

Connected through hyperedge HE-3 (induced by source paper "on complexity of flooding games on graphs with interval representations"):
  with members:
    - "spanning trees and the complexity of flood filling games"
    - "the complexity of free flood it on 2ixn boards"
    - "the complexity of flood filling games on graphs"
    - "an algorithmic analysis of the honey bee game"
    - "2 free flood it is polynomial"

Connected through hyperedge HE-4 (induced by source paper "the complexity of the puzzles of final fantasy xiii 2"):
  with members:
    - "gaming is a hard job but someone has to do it"
    - "tetris is hard even to approximate"
    - "the complexity of clickomania"

Connected through hyperedge HE-5 (induced by source paper "the complexity of flood filling games on graphs"):
  with members:
    - "the complexity of free flood it on 2ixn boards"
    - "an algorithmic analysis of the honey bee game"

Connected through hyperedge HE-6 (induced by source paper "an algorithmic analysis of the honey bee game"):
  with members:
    - "playing games with algorithms algorithmic combinatorial game theory"
    - "the complexity of clickomania"

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)