Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Sofia Brenner, Linda Kleist, Torsten Mütze, Christian Rieck, and Francesco Verciani. Disproving Two Conjectures on the Hamiltonicity of Venn Diagrams. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 22:1-22:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{brenner_et_al:LIPIcs.SoCG.2026.22,
author = {Brenner, Sofia and Kleist, Linda and M\"{u}tze, Torsten and Rieck, Christian and Verciani, Francesco},
title = {{Disproving Two Conjectures on the Hamiltonicity of Venn Diagrams}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {22:1--22:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.22},
URN = {urn:nbn:de:0030-drops-258285},
doi = {10.4230/LIPIcs.SoCG.2026.22},
annote = {Keywords: Venn diagram, Winkler’s conjecture, Hamilton cycle, perfect matching, hypercube}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Bruce W. Brewer and Haitao Wang. Shortest Paths in Geodesic Unit-Disk Graphs. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 23:1-23:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{brewer_et_al:LIPIcs.SoCG.2026.23,
author = {Brewer, Bruce W. and Wang, Haitao},
title = {{Shortest Paths in Geodesic Unit-Disk Graphs}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {23:1--23:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.23},
URN = {urn:nbn:de:0030-drops-258297},
doi = {10.4230/LIPIcs.SoCG.2026.23},
annote = {Keywords: unit-disk graph, geodesic distance, shortest paths, geodesic Voronoi diagrams, range emptiness queries, dynamic data structures}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Jacobus Conradi, Ivor van der Hoog, and Eva Rotenberg. On Computing the (Exact) Fréchet Distance with a Frog. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 35:1-35:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{conradi_et_al:LIPIcs.SoCG.2026.35,
author = {Conradi, Jacobus and van der Hoog, Ivor and Rotenberg, Eva},
title = {{On Computing the (Exact) Fr\'{e}chet Distance with a Frog}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {35:1--35:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.35},
URN = {urn:nbn:de:0030-drops-258414},
doi = {10.4230/LIPIcs.SoCG.2026.35},
annote = {Keywords: Algorithms engineering, Fr\'{e}chet distance}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Giordano Da Lozzo, Fabrizio Frati, and Ignaz Rutter. Upward Book Embeddings of Partitioned Digraphs. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 36:1-36:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{dalozzo_et_al:LIPIcs.SoCG.2026.36,
author = {Da Lozzo, Giordano and Frati, Fabrizio and Rutter, Ignaz},
title = {{Upward Book Embeddings of Partitioned Digraphs}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {36:1--36:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.36},
URN = {urn:nbn:de:0030-drops-258424},
doi = {10.4230/LIPIcs.SoCG.2026.36},
annote = {Keywords: upward book embeddings, partitioned digraphs, SPQ-trees, 2-trees}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Chengyuan Deng, Jie Gao, Kevin Lu, Feng Luo, and Cheng Xin. Locality Sensitive Hashing in Hyperbolic Space. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 39:1-39:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{deng_et_al:LIPIcs.SoCG.2026.39,
author = {Deng, Chengyuan and Gao, Jie and Lu, Kevin and Luo, Feng and Xin, Cheng},
title = {{Locality Sensitive Hashing in Hyperbolic Space}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {39:1--39:19},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.39},
URN = {urn:nbn:de:0030-drops-258454},
doi = {10.4230/LIPIcs.SoCG.2026.39},
annote = {Keywords: Locality Sensitive Hashing, Hyperbolic Geometry, Dimension Reduction, Approximate Nearest Neighbor Search}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Loïc Dubois. Computing the Intrinsic Delaunay Triangulation of a Closed Polyhedral Surface. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 40:1-40:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{dubois:LIPIcs.SoCG.2026.40,
author = {Dubois, Lo\"{i}c},
title = {{Computing the Intrinsic Delaunay Triangulation of a Closed Polyhedral Surface}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {40:1--40:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.40},
URN = {urn:nbn:de:0030-drops-258460},
doi = {10.4230/LIPIcs.SoCG.2026.40},
annote = {Keywords: Polyhedral surface, intrinsic Delaunay triangulation, algorithmic complexity}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Sándor P. Fekete, Prahlad Narasimhan Kasthurirangan, Phillip Keldenich, Fabian Kollhoff, Chek-Manh Loi, and Michael Perk. Line Segment Visibility in Simple Polygons: Exact, Robust, Scalable Computation and Applications. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 45:1-45:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{fekete_et_al:LIPIcs.SoCG.2026.45,
author = {Fekete, S\'{a}ndor P. and Kasthurirangan, Prahlad Narasimhan and Keldenich, Phillip and Kollhoff, Fabian and Loi, Chek-Manh and Perk, Michael},
title = {{Line Segment Visibility in Simple Polygons: Exact, Robust, Scalable Computation and Applications}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {45:1--45:19},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.45},
URN = {urn:nbn:de:0030-drops-258516},
doi = {10.4230/LIPIcs.SoCG.2026.45},
annote = {Keywords: Visibility, line segments, link distance, window partition, computation, implementation, robustness, scalability, exactness, CGAL}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Sándor P. Fekete, Rouven Kniep, Dominik Krupke, and Michael Perk. A Branch-And-Bound Algorithm for the Traveling Salesman Problem with Difficult Neighborhoods. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 46:1-46:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{fekete_et_al:LIPIcs.SoCG.2026.46,
author = {Fekete, S\'{a}ndor P. and Kniep, Rouven and Krupke, Dominik and Perk, Michael},
title = {{A Branch-And-Bound Algorithm for the Traveling Salesman Problem with Difficult Neighborhoods}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {46:1--46:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.46},
URN = {urn:nbn:de:0030-drops-258529},
doi = {10.4230/LIPIcs.SoCG.2026.46},
annote = {Keywords: Geometric optimization, geometric covering, TSP with neighborhoods, exact algorithms, algorithm engineering}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Marc Fersztand and Jan Jendrysiak. Computing the Skyscraper Invariant. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 47:1-47:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{fersztand_et_al:LIPIcs.SoCG.2026.47,
author = {Fersztand, Marc and Jendrysiak, Jan},
title = {{Computing the Skyscraper Invariant}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {47:1--47:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.47},
URN = {urn:nbn:de:0030-drops-258535},
doi = {10.4230/LIPIcs.SoCG.2026.47},
annote = {Keywords: Topological Data Analysis, Multiparameter Persistence, Persistence, Harder-Narasimhan Filtration, Skyscraper Invariant}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Fedor V. Fomin, Petr A. Golovach, M. S. Ramanujan, and Saket Saurabh. Algorithms for Euclidean Distance Matrix Completion: Exploiting Proximity to Triviality. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 49:1-49:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{fomin_et_al:LIPIcs.SoCG.2026.49,
author = {Fomin, Fedor V. and Golovach, Petr A. and Ramanujan, M. S. and Saurabh, Saket},
title = {{Algorithms for Euclidean Distance Matrix Completion: Exploiting Proximity to Triviality}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {49:1--49:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.49},
URN = {urn:nbn:de:0030-drops-258552},
doi = {10.4230/LIPIcs.SoCG.2026.49},
annote = {Keywords: Parameterized Complexity, Euclidean Embedding, Polynomial Compression}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Mustafa Alper Gunes and Assaf Naor. Optimal Randomized Clustering of Matrices. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 56:1-56:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{gunes_et_al:LIPIcs.SoCG.2026.56,
author = {Gunes, Mustafa Alper and Naor, Assaf},
title = {{Optimal Randomized Clustering of Matrices}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {56:1--56:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.56},
URN = {urn:nbn:de:0030-drops-258624},
doi = {10.4230/LIPIcs.SoCG.2026.56},
annote = {Keywords: Clustering, Unitarily Invariant Matrix Norms, Oracle Polynomial Time Approximation Algorithms for Radii of Convex Bodies, Extension of Lipschitz Functions, Random Matrices, Spectrum of the Laplacian with Dirichlet Boundary Conditions, Reverse Isoperimetry}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Yaara Jahn and Orit E. Raz. Improved Bound for the k-Variate Elekes-Rónyai Theorem. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 59:1-59:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{jahn_et_al:LIPIcs.SoCG.2026.59,
author = {Jahn, Yaara and Raz, Orit E.},
title = {{Improved Bound for the k-Variate Elekes-R\'{o}nyai Theorem}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {59:1--59:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.59},
URN = {urn:nbn:de:0030-drops-258663},
doi = {10.4230/LIPIcs.SoCG.2026.59},
annote = {Keywords: Polynomial Expansion, Elekes-R\'{o}nyai theorem}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Balázs Keszegh, Andrew Suk, Gábor Tardos, and Ji Zeng. Unavoidable Patterns and Plane Paths in Dense Topological Graphs. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 63:1-63:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{keszegh_et_al:LIPIcs.SoCG.2026.63,
author = {Keszegh, Bal\'{a}zs and Suk, Andrew and Tardos, G\'{a}bor and Zeng, Ji},
title = {{Unavoidable Patterns and Plane Paths in Dense Topological Graphs}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {63:1--63:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.63},
URN = {urn:nbn:de:0030-drops-258706},
doi = {10.4230/LIPIcs.SoCG.2026.63},
annote = {Keywords: graph drawing, topological graph, bipartite geometric graph, forbidden subgraph, extremal graph, thrackle}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Joost van der Laan, Frank Staals, and Lorenzo Theunissen. Approximate Dynamic Nearest Neighbor Searching in a Polygonal Domain. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 69:1-69:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{vanderlaan_et_al:LIPIcs.SoCG.2026.69,
author = {van der Laan, Joost and Staals, Frank and Theunissen, Lorenzo},
title = {{Approximate Dynamic Nearest Neighbor Searching in a Polygonal Domain}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {69:1--69:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.69},
URN = {urn:nbn:de:0030-drops-258769},
doi = {10.4230/LIPIcs.SoCG.2026.69},
annote = {Keywords: dynamic data structure, nearest neighbor search, polygonal domain}
}
Published in: LIPIcs, Volume 367, 42nd International Symposium on Computational Geometry (SoCG 2026)
Hung Le, Shay Solomon, Cuong Than, Csaba D. Tóth, and Tianyi Zhang. Approximating Euclidean Shallow-Light Trees. In 42nd International Symposium on Computational Geometry (SoCG 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 367, pp. 71:1-71:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)
@InProceedings{le_et_al:LIPIcs.SoCG.2026.71,
author = {Le, Hung and Solomon, Shay and Than, Cuong and T\'{o}th, Csaba D. and Zhang, Tianyi},
title = {{Approximating Euclidean Shallow-Light Trees}},
booktitle = {42nd International Symposium on Computational Geometry (SoCG 2026)},
pages = {71:1--71:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-418-5},
ISSN = {1868-8969},
year = {2026},
volume = {367},
editor = {Ahn, Hee-Kap and Hoffmann, Michael and Nayyeri, Amir},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2026.71},
URN = {urn:nbn:de:0030-drops-258789},
doi = {10.4230/LIPIcs.SoCG.2026.71},
annote = {Keywords: geometric network design, optimization, shallow-light tree, Steiner point}
}