Television commercial scheduling is a generalised form of bin-packing problem, but the bins are rather small, leaving the complexity of the problem unclear. This paper shows that if spot-fixing is… (More)

The word problem for confluent Thue systems is linear-time and for almost confluent systems it is PSPACE-complete. Here we consider a single length-preserving rule, of the form xy ↔ yx, whose word… (More)

A question about 2-complexes, analogous to graph planarity, is whether they can be embedded in 3 dimensions. This is a difficult question. Also, whereas planar graphs always admit straightedge… (More)

Lee and Drysdale [13] and Sharir [16] have given suboptimal algorithms for computing the Voronoi diagrams of line-segments or discs in the plane. This paper adapts their methods to constructing the… (More)

An interesting question about planar graphs is whether they admit plane embeddings in which every bounded face is convex. Stein [10] gave as a necessary and sufficient condition that every face… (More)

It is fairly easy to show that every regular set is an almost-confluent congruential language (ACCL), and it is known [3] that every regular set is a Church-Rosser congruential language (CRCL).… (More)

It is known that to traverse a binary tree in inorder, by repeated splay-to-root, uses O(n) rotations. Estimates vary from 15n to 4.5n in proofs of varying length and difficulty. We present a fairly… (More)

This paper studies local properties of Voronoi diagrams of sets of disjoint compact convex sites in R. It is established that bisectors are C surfaces and trisectors are C curves, and that as a point… (More)

Notation: red for definition or first use, blue for explanations. Alphabet Σ any finite set Free monoid Σ * semigroup with identity — under concatenation