human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "token swapping on trees"):
  Abstract: The input to the token swapping problem is a graph with vertices $v_1, v_2, \ldots, v_n$, and $n$ tokens with labels $1, 2, \ldots, n$, one on each vertex. The goal is to get token $i$ to vertex $v_i$ for all $i= 1, \ldots, n$ using a minimum number of \emph{swaps}, where a swap exchanges the tokens on the endpoints of an edge. #R##N#Token swapping on a tree, also known as "sorting with a transposition tree", is not known to be in P nor NP-complete. We present some partial results: #R##N#1. An optimum swap sequence may need to perform a swap on a leaf vertex that has the correct token (a "happy leaf"), disproving a conjecture of Vaughan. #R##N#2. Any algorithm that fixes happy leaves---as all known approximation algorithms for the problem do---has approximation factor at least $4/3$. Furthermore, the two best-known 2-approximation algorithms have approximation factor exactly 2. #R##N#3. A generalized problem---weighted coloured token swapping---is NP-complete on trees, but solvable in polynomial time on paths and stars. In this version, tokens and vertices have colours, and colours have weights. The goal is to get every token to a vertex of the same colour, and the cost of a swap is the sum of the weights of the two tokens involved.

Includes members:
  Member "swapping colored tokens on graphs":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "complexity of token swapping and its variants")
  Member "the time complexity of permutation routing via matching token swapping and a variant":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "shortest reconfiguration of perfect matchings via alternating cycles")
  Member "the time complexity of the token swapping problem and its parallel variants":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "finding optimal solutions to token swapping by conflict based search and reduction to sat")
  Member "approximation and hardness for token swapping":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "reconfiguration of connected graph partitions")
  Member "pebble games proof complexity and time space trade offs":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "nullstellensatz size degree trade offs from reversible pebbling")
  Member "the complexity of change":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "dominating sets reconfiguration under token sliding")
  Member "an efficient algorithm for the diameter of cayley graphs generated by transposition trees":
    also connected through other hyperedges:
      (none)
  Member "pancake flipping is hard":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "shortest reconfiguration of perfect matchings via alternating cycles")

Question: Please tell me which class the source paper 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)