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FSTTCS
2008
Springer

STCON in Directed Unique-Path Graphs

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STCON in Directed Unique-Path Graphs
ABSTRACT. We study the problem of space-efficient polynomial-time algorithms for directed stconnectivity (STCON). Given a directed graph G, and a pair of vertices s, t, the STCON problem is to decide if there exists a path from s to t in G. For general graphs, the best polynomial-time algorithm for STCON uses space that is only slightly sublinear. However, for special classes of directed graphs, polynomial-time poly-logarithmic-space algorithms are known for STCON. In this paper, we continue this thread of research and study a class of graphs called unique-path graphs with respect to source s, where there is at most one simple path from s to any vertex in the graph. For these graphs, we give a polynomial-time algorithm that uses ˜O(nε) space for any constant ε ∈ (0, 1]. We also give a polynomial-time, ˜O(nε)-space algorithm to recognize unique-path graphs. Unique-path graphs are related to configuration graphs of unambiguous log-space computations, but they can have some direc...
Sampath Kannan, Sanjeev Khanna, Sudeepa Roy
Added 09 Nov 2010
Updated 09 Nov 2010
Type Conference
Year 2008
Where FSTTCS
Authors Sampath Kannan, Sanjeev Khanna, Sudeepa Roy
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