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- Björn Brodén, Mikael Hammar, Bengt J. Nilsson
- CCCG
- 2001

- Mikael Hammar, Bengt J. Nilsson
- ICALP
- 1999

We study the approximation complexity of certain kinetic variants of the Trav-eling Salesman Problem where we consider instances in which each point moves with a xed constant speed in a xed direction. We prove the following results. 1. If the points all move with the same velocity, then there is a PTAS for the Kinetic TSP. 2. The Kinetic TSP cannot be… (More)

- Joachim Gudmundsson, Mikael Hammar, Marc J. van Kreveld
- Comput. Geom.
- 2000

- Pankaj K. Agarwal, Mark de Berg, Joachim Gudmundsson, Mikael Hammar, Herman J. Haverkort
- Discrete & Computational Geometry
- 2001

A box-tree is a \ifasci so-called \emph{bounding-volume hierarchy} \else bounding-volume hierarchy \fi that uses axis-aligned boxes as bounding volumes. The query complexity of a box-tree with respect to a given type of query is the maximum number of nodes visited when answering such a query. We describe several new algorithms for constructing box-trees… (More)

We propose routing schemes that optimize the average number of hops for lookup requests in Peer–to–Peer (P2P) systems without adding any overhead to the system. Our work is inspired by the recently introduced variation of greedy routing, called neighbor–of–neighbor (NoN), which allows to get optimal average path length with respect to the degree. Our… (More)

- Luisa Gargano, Mikael Hammar
- Discrete Mathematics
- 2009

- Luisa Gargano, Mikael Hammar, Anna Pagh
- 18th International Parallel and Distributed…
- 2004

Summary form only given. We study on-demand source initiated protocols for mobile wireless networks. In particular, we study the flooding procedure commonly used by these protocols to set up temporary communication paths. The benefit of the flooding technique is its generosity regarding changes in network structure. On the other hand, each time a message is… (More)

- Luisa Gargano, Mikael Hammar, Pavol Hell, Ladislav Stacho, Ugo Vaccaro
- Discrete Mathematics
- 2004

Motivated by a problem in the design of optical networks, we ask when a graph has a spanning spider (subdivision of a star), or, more generally, a spanning tree with a bounded number of branch vertices. We investigate the existence of these spanning subgraphs in analogy to classical studies of Hamiltonicity.

- Mikael Hammar, Bengt J. Nilsson
- FCT
- 1997

A watchman route in a polygon P is a route inside P such that each point in the interior of P is visible from at least one point along the route. The objective of the shortest watchman route problem is to minimize the length of the watchman route for a given polygon. In 1991 Chin and Ntafos claimed an O(n 4) algorithm, solving the shortest watchman route… (More)