Abstract
A rectangular dual of a graph $G$ is a contact
representation of $G$ by axis-aligned rectangles
such that (i) no four rectangles share a point and
(ii) the union of all rectangles is a rectangle.
The partial representation extension problem
for rectangular duals asks whether a given partial
rectangular dual can be extended to a rectangular
dual, that is, whether there exists a rectangular
dual where some vertices are represented by
prescribed rectangles. The simultaneous
representation problem for rectangular duals asks
whether two (or more) given graphs that share a
subgraph admit rectangular duals that coincide on
the shared subgraph. Combinatorially, a rectangular
dual can be described by a regular edge labeling
(REL), which determines the orientations of the
rectangle contacts. We describe linear-time
algorithms for the partial representation extension
problem and the simultaneous representation problem
for rectangular duals when each input graph is given
together with a REL. Both algorithms are based on
formulations as linear programs, yet they have
geometric interpretations and can be seen as
extensions of the classic algorithm by Kant and He
that computes a rectangular dual for a given graph.
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