On 15.11.2007 at 12.20 in S5, there is the following noon lecture:
On tractability of Cops and Robbers game
The Cops and Robbers game is played on undirected graphs where a group of cops tries to catch a robber. The game was defined independently by Winkler-Nowakowski and Quilliot in the 1980s and since that time has been studied intensively. Despite of that, its computation complexity is still an open question. We prove that computing the minimum number of cops that can catch a robber on a given graph is NP-hard. Also we show that the parameterized version of the problem is W-hard. Our proof can be extended for to the variant of the game where the robber can move $s$ times faster than cops. We also provide a number of algorithmic and complexity results on classes of chordal graphs and on graphs of bounded cliquewidth. For example, we show that when the velocity of the robber is twice cop's velocity, the problem is NP-hard on split graphs, while it is polynomial time solvable on split graphs when players posses the same speed. Finally, we establish that on graphs of bounded cliquewidth (this class of graphs, for example, contain graphs of bounded treewidth), the problem is solvable in polynomial time in the case the robber's speed is at most twice the speed of cops.
The talk is based on paper: Fedor V. Fomin, Petr A. Golovach, Jan Kratochvil, On tractability of Cops and Robbers game.
Modified: 19. 10. 2010