## Abstract

Let D be a set of n pairwise disjoint unit disks in the plane. We describe how

to build a data structure for D so that for any point set P containing exactly one point

from each disk, we can quickly nd the onion decomposition (convex layers) of P.

Our data structure can be built in O(n log n) time and has linear size. Given P, we

can nd its onion decomposition in O(n log k) time, where k is the number of layers. We

also provide a matching lower bound.

Our solution is based on a recursive space decomposition, combined with a fast

algorithm to compute the union of two disjoint onion decompositions.

to build a data structure for D so that for any point set P containing exactly one point

from each disk, we can quickly nd the onion decomposition (convex layers) of P.

Our data structure can be built in O(n log n) time and has linear size. Given P, we

can nd its onion decomposition in O(n log k) time, where k is the number of layers. We

also provide a matching lower bound.

Our solution is based on a recursive space decomposition, combined with a fast

algorithm to compute the union of two disjoint onion decompositions.

Original language | English |
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Pages (from-to) | 1-13 |

Number of pages | 13 |

Journal | Journal of Computational Geometry |

Volume | 5 |

Issue number | 1 |

Publication status | Published - 2014 |

## Keywords

- CG, DS, IMP, CH