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Tanglegrams are formed by taking two rooted binary trees $T$ and $S$ with the same number of leaves and uniquely matching each leaf in $T$ with a leaf in $S$. They are usually represented using layouts, which embed the trees and the…

Combinatorics · Mathematics 2022-06-14 Kevin Liu

A tanglegram consists of two binary rooted trees with the same number of leaves and a perfect matching between the leaves of the trees. We show that the two halves of a random tanglegram essentially look like two independently chosen random…

Combinatorics · Mathematics 2016-04-08 Matjaž Konvalinka , Stephan Wagner

A tanglegram consists of two rooted binary trees with the same number of leaves and a perfect matching between the leaves of the trees. Given a size-$n$ tanglegram, i.e., a tanglegram for two trees with $n$ leaves, a multiset of induced…

Combinatorics · Mathematics 2025-08-18 Ann Clifton , Eva Czabarka , Kevin Liu , Sarah Loeb , Utku Okur , Laszlo Szekely , Kristina Wicke

A tanglegram is a pair of binary trees with the same set of leaves. Unlabeled tanglegrams were counted recently by Billey, Konvalinka, and Matsen, who also proposed the problem of counting several variations of unlabeled tanglegrams…

Combinatorics · Mathematics 2021-07-06 Ira M. Gessel

A tanglegram $\cal T$ consists of two rooted binary trees with the same number of leaves, and a perfect matching between the two leaf sets. In a layout, the tanglegrams is drawn with the leaves on two parallel lines, the trees on either…

Combinatorics · Mathematics 2023-07-11 Éva Czabarka , Junsheng Liu , László A. Székely

A tanglegram of size n is a graph formed from two rooted binary trees with n leaves each and a perfect matching between their leaf sets. Tanglegrams are used to model co-evolution in various settings. A tanglegram layout is a straight line…

Combinatorics · Mathematics 2025-05-02 Éva Czabarka , Alec Helm , László Székely

Tanglegrams are special graphs that consist of a pair of rooted binary trees with the same number of leaves, and a perfect matching between the two leaf-sets. These objects are of use in phylogenetics and are represented with straightline…

A tanglegram consists of two rooted binary trees and a perfect matching between their leaves, and a planar tanglegram is one that admits a layout with no crossings. We show that the problem of generating planar tanglegrams uniformly at…

Combinatorics · Mathematics 2023-04-13 Alexander E. Black , Kevin Liu , Alex Mcdonough , Garrett Nelson , Michael C. Wigal , Mei Yin , Youngho Yoo

A binary tanglegram is a pair <S,T> of binary trees whose leaf sets are in one-to-one correspondence; matching leaves are connected by inter-tree edges. For applications, for example in phylogenetics or software engineering, it is required…

Data Structures and Algorithms · Computer Science 2009-05-15 Martin Nöllenburg , Danny Holten , Markus Völker , Alexander Wolff

Tanglegrams are a special class of graphs appearing in applications concerning cospeciation and coevolution in biology and computer science. They are formed by identifying the leaves of two rooted binary trees. We give an explicit formula…

Combinatorics · Mathematics 2015-07-20 Sara Billey , Matjaž Konvalinka , Frederick A Matsen

Tanglegrams are drawings of two rooted binary phylogenetic trees and a matching between their leaf sets. The trees are drawn crossing-free on opposite sides with their leaf sets facing each other on two vertical lines. Instead of minimizing…

Data Structures and Algorithms · Computer Science 2023-05-09 Alexander Dobler , Martin Nöllenburg

A 2-tree is a graph that can be formed by starting with a triangle and iterating the operation of making a new vertex adjacent to two adjacent vertices of the existing graph. Leizhen Cai asked in 1995 whether every maximal planar graph…

Combinatorics · Mathematics 2022-03-22 Allan Bickle

Packing graphs is a combinatorial problem where several given graphs are being mapped into a common host graph such that every edge is used at most once. In the planar tree packing problem we are given two trees T1 and T2 on n vertices and…

Computational Geometry · Computer Science 2016-03-28 Markus Geyer , Michael Hoffmann , Michael Kaufmann , Vincent Kusters , Csaba D. Tóth

It is proven that a connected graph is planar if and only if all its cocycles with at least four edges are "grounded" in the graph. The notion of grounding of this planarity criterion, which is purely combinatorial, stems from the intuitive…

Combinatorics · Mathematics 2014-10-22 K. Dosen , Z. Petric

Kuratowski's theorem says that the minimal (under subgraph containment) graphs that are not planar are the subdivisions of $K_5$ and of $K_{3,3}$. Here we study the minimal (under subdigraph containment) strongly-connected digraphs that are…

Combinatorics · Mathematics 2025-03-11 Stephen Bartell , Paul Seymour

Tangle structure trees, introduced in [3], offer a unified data structure that displays all the tangles of a graph or data set together with certificates for the non-existence of any other tangles, either locally or overall. In this paper…

Combinatorics · Mathematics 2026-03-19 Hanno von Bergen , Reinhard Diestel

A plane graph is called a rectangular graph if each of its edges can be oriented either horizontally or vertically, each of its interior regions is a four-sided region and all interior regions can be fitted in a rectangular enclosure. Only…

Combinatorics · Mathematics 2021-02-11 Vinod Kumar , Krishnendra Shekhawat

A \emph{binary tanglegram} is a drawing of a pair of rooted binary trees whose leaf sets are in one-to-one correspondence; matching leaves are connected by inter-tree edges. For applications, for example, in phylogenetics, it is essential…

Computational Geometry · Computer Science 2010-09-17 Kevin Buchin , Maike Buchin , Jaroslaw Byrka , Martin Nöllenburg , Yoshio Okamoto , Rodrigo I. Silveira , Alexander Wolff

Contrary to the expectation arising from the tanglegram Kuratowski theorem of \'E. Czabarka, L.A. Sz\'ekely and S. Wagner [SIAM J. Discrete Math. 31(3): 1732--1750, (2017)], we construct an infinite antichain of planar tanglegrams with…

Combinatorics · Mathematics 2020-07-15 Éva Czabarka , Stephen J. Smith , László A. Székely

This paper considers the problem of showing that every pair of binary trees with the same number of leaves parses a common word under a certain simple grammar. We enumerate the common parse words for several infinite families of tree pairs…

Combinatorics · Mathematics 2014-04-18 Bobbe Cooper , Eric Rowland , Doron Zeilberger
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