
Summary: A graph is \(B_k\)-VPG when it has an intersection representation by paths in a rectangular grid with at most \(k\) bends (turns). It is known that all planar graphs are \(B_3\)-VPG and this was conjectured to be tight. We disprove this conjecture by showing that all planar graphs are \(B_2\)-VPG. We also show that the 4-connected planar graphs constitute a subclass of the intersection graphs of Z-shapes (i.e., a special case of \(B_2\)-VPG). Additionally, we demonstrate that a \(B_2\)-VPG representation of a planar graph can be constructed in \(O(n^{3/2})\) time. We further show that the triangle-free planar graphs are contact graphs of: L-shapes, {\(\Gamma\)}-shapes, vertical segments, and horizontal segments (i.e., a special case of contact \(B_1\)-VPG). From this proof we obtain a new proof that bipartite planar graphs are a subclass of 2-DIR.
Graph algorithms (graph-theoretic aspects), Graph representations (geometric and intersection representations, etc.), Planar graphs; geometric and topological aspects of graph theory
Graph algorithms (graph-theoretic aspects), Graph representations (geometric and intersection representations, etc.), Planar graphs; geometric and topological aspects of graph theory
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