Title
Complexity of searching an immobile hider in a graph
Abstract
We study the computational complexity of certain search-hide games on a graph. There are two players, called searcher and hider. The hider is immobile and hides in one of the nodes of the graph. The searcher selects a starting node and a search path of length at most k . His objective is to detect the hider, which he does with certainty if he visits the node chosen for hiding. Finding the optimal randomized strategies in this zero-sum game defines a fractional path covering problem and its dual, a fractional packing problem. If the length k of the search path is arbitrary, then the problem is NP-hard. The problem remains NP-hard if the searcher may freely revisit nodes that he has seen before. In that case, the searcher selects a connected subgraph of k nodes rather than a path of k nodes. If k is logarithmic in the number of nodes of the graph, then the problem can be solved in polynomial time. This is shown using a recent technique called color-coding due to Alon, Yuster and Zwick. The same results hold for edges instead of nodes, that is, if the hider hides in an edge and the searcher searches k edges on a path or on a connected subgraph.
Year
DOI
Venue
1997
10.1016/S0166-218X(97)00011-5
Discrete Applied Mathematics
Keywords
Field
DocType
game theory,immobile hider,np-completeness,covering and packing,graph search,polynomial time,np completeness,computational complexity,zero sum game
Graph theory,Discrete mathematics,Graph,Combinatorics,Packing problems,Game theory,Zero-sum game,Logarithm,Time complexity,Mathematics,Computational complexity theory
Journal
Volume
Issue
ISSN
78
1-3
Discrete Applied Mathematics
Citations 
PageRank 
References 
9
0.81
9
Authors
2
Name
Order
Citations
PageRank
Bernhard von Stengel127538.51
Ralph Werchner21139.56