文摘
We present a technique for representing bounded-degree planar graphs in a succinct fashion while permitting I/O-efficient traversal of paths. Using our representation, a graph with N vertices, (In this paper \(\lg {N}\) denotes \(\log _2{N}\)) each with an associated key of \(q= \mathrm {O}\left( \lg N\right) \) bits, can be stored in \(Nq+ \mathrm {O}\left( N\right) + \mathrm {o}\left( Nq\right) \) bits and traversing a path of length K takes \(\mathrm {O}\left( K / \lg B\right) \) I/Os, where B denotes the disk block size. By applying our construction to the dual of a terrain represented as a triangular irregular network, we can represent the terrain in the above space bounds and support path traversals on the terrain using \(\mathrm {O}\left( K / \lg B\right) \) I/Os, where K is the number of triangles visited by the path. This is useful for answering a number of queries on the terrain, such as reporting terrain profiles, trickle paths, and connected components.