## Abstract

In a graph G whose vertices contain pebbles, a pebbling move uv removes two pebbles from u and adds one pebble to a neighbor v of u. The optimal pebbling number π̂(G) is the minimum k such that there exists a distribution of k pebbles to G so that for any target vertex r in G, there is a sequence of pebbling moves which places a pebble on r. The pebbling number π(G) is the minimum k such that for all distributions of k pebbles to G and for any target vertex r, there is a sequence of pebbling moves which places a pebble on r. We explore the computational complexity of computing π̂(G) and π(G). In particular, we show that deciding whether π̂(G) ≤ k is NP-complete. Furthermore, we prove that deciding whether π(G) ≤ k is ∏_{2}^{P}-complete and therefore both NP-hard and coNP-hard. Additionally, we provide a characterization of when an unordered set of pebbling moves can be ordered to form a valid sequence of pebbling moves.

Original language | English (US) |
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Pages (from-to) | 769-798 |

Number of pages | 30 |

Journal | SIAM Journal on Discrete Mathematics |

Volume | 20 |

Issue number | 3 |

DOIs | |

State | Published - 2006 |

## Keywords

- Complexity
- Graph pebbling
- ∏-completeness

## ASJC Scopus subject areas

- General Mathematics