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A (possibly degenerate) drawing of a graph G in the plane is approximable by an embedding if it can be turned into an embedding by an arbitrarily small perturbation. We show that testing, whether a drawing of a planar graph G in the plane is approximable by an embedding, can be carried out in polynomial time, if a desired embedding of G belongs to a fixed isotopy class, i.e., the rotation system (or equivalently the faces) of the embedding of G and the choice of outer face are fixed. In other words, we show that c-planarity with embedded pipes is tractable for graphs with fixed embeddings. To the best of our knowledge an analogous result was previously known essentially only when G is a cycle.
@InProceedings{fulek:LIPIcs.ISAAC.2017.34,
author = {Fulek, Radoslav},
title = {{Embedding Graphs into Embedded Graphs}},
booktitle = {28th International Symposium on Algorithms and Computation (ISAAC 2017)},
pages = {34:1--34:12},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-054-5},
ISSN = {1868-8969},
year = {2017},
volume = {92},
editor = {Okamoto, Yoshio and Tokuyama, Takeshi},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2017.34},
URN = {urn:nbn:de:0030-drops-82234},
doi = {10.4230/LIPIcs.ISAAC.2017.34},
annote = {Keywords: Graph embedding, C-planarity, Weakly simple polygons}
}