Tree Drawings Revisited

We make progress on a number of open problems concerning the area requirement for drawing trees on a grid. We prove that 1) every tree of size n (with arbitrarily large degree) has a straight-line drawing with area n2^{O(sqrt{log log n log log log n})}, improving the longstanding O(n log n) bound; 2) every tree of size n (with arbitrarily large degree) has a straight-line upward drawing with area n sqrt{log n}(log log n)^{O(1)}, improving the longstanding O(n log n) bound; 3) every binary tree of size n has a straight-line orthogonal drawing with area n2^{O(log^*n)}, improving the previous O(n log log n) bound by Shin, Kim, and Chwa (1996) and Chan, Goodrich, Kosaraju, and Tamassia (1996); 4) every binary tree of size n has a straight-line order-preserving drawing with area n2^{O(log^*n)}, improving the previous O(n log log n) bound by Garg and Rusu (2003); 5) every binary tree of size n has a straight-line orthogonal order-preserving drawing with area n2^{O(sqrt{log n})}, improving the O(n^{3/2}) previous bound by Frati (2007)

On Upward Drawings of Trees on a Given Grid

Computing a minimum-area planar straight-line drawing of a graph is known to be NP-hard for planar graphs, even when restricted to outerplanar graphs. However, the complexity question is open for trees. Only a few hardness results are known for straight-line drawings of trees under various restrictions such as edge length or slope constraints. On the other hand, there exist polynomial-time algorithms for computing minimum-width (resp., minimum-height) upward drawings of trees, where the height (resp., width) is unbounded. In this paper we take a major step in understanding the complexity of the area minimization problem for strictly-upward drawings of trees, which is one of the most common styles for drawing rooted trees. We prove that given a rooted tree $T$ and a $W\times H$ grid, it is NP-hard to decide whether $T$ admits a strictly-upward (unordered) drawing in the given grid.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Small Superpatterns for Dominance Drawing

We exploit the connection between dominance drawings of directed acyclic graphs and permutations, in both directions, to provide improved bounds on the size of universal point sets for certain types of dominance drawing and on superpatterns for certain natural classes of permutations. In particular we show that there exist universal point sets for dominance drawings of the Hasse diagrams of width-two partial orders of size O(n^{3/2}), universal point sets for dominance drawings of st-outerplanar graphs of size O(n\log n), and universal point sets for dominance drawings of directed trees of size O(n^2). We show that 321-avoiding permutations have superpatterns of size O(n^{3/2}), riffle permutations (321-, 2143-, and 2413-avoiding permutations) have superpatterns of size O(n), and the concatenations of sequences of riffles and their inverses have superpatterns of size O(n\log n). Our analysis includes a calculation of the leading constants in these bounds.Comment: ANALCO 2014, This version fixes an error in the leading constant of the 321-superpattern siz

Study and implementation of some tree drawing algorithms

Graph drawing deals with the geometric representation of graphs [1]. Data representation problems that require graph models can be better understood when visualized with appropriate graph drawings. The typical data structure for modeling hierarchical information is a tree whose vertices represent entities and whose edges correspond to relationships between entities. Algorithms for drawing trees are typically based on some graph-theoretic insight into the structure of the tree. It is characterized by the fact that in the drawings produced, the nodes at the same distance from the root are horizontally aligned [1]. This level-based approach can be used for both binary and general trees. Algorithms based on this approach involve some issues that lead to aesthetically wider than necessary drawings. I implemented “A Naïve Tree Drawing Algorithm” [2] as part of an independent study. This will serve as a basis and an introduction to this proposed thesis. In this thesis, we develop some tree drawing algorithms and a planarity drawing algorithm in terms of constructing a new pseudocode for each algorithm. Also, we focus on the theoretical graphic insight to the structure of the tree by building a drawing application for each algorithm. These applications provide an important view of the properties of drawing trees. In addition, these algorithms are implemented in a GUI (JEdit) that reflects an efficient aesthetic drawing. The input graph is checked to verify that it is a tree. The user sees an error message otherwise. These algorithms allow the user to select the root in an input tree. This leads to a better understanding of the algorithms. Most of these algorithms calculate the levels of the tree and the number of the nodes in each level. These algorithms are : the “Recursive Algorithm for Binary Trees” from [3], which has many steps, the “A Node-Positioning Algorithm for General Trees” from [4], the “Area-Efficient Order-Preserving Planar Straight-Line Drawings of Ordered Trees” from Section 3 of [5], and “Planarity Drawing Algorithm” from Section 2 of [6].Thesis (M.S.)Department of Computer ScienceGraph drawing basics and (GUI) for graph theory -- A naive tree drawing algorithm -- Recursive algorithm for binary trees -- A node positioning algorithm for general trees -- Area-efficient order-preserving planar straight-line drawings of ordered trees -- Planarity drawing algorithm

How to fit a tree in a box

We study compact straight-line embeddings of trees. We show that perfect binary trees can be embedded optimally: a tree with n nodes can be drawn on a vn by vn grid. We also show that testing whether a given rooted binary tree has an upward embedding with a given combinatorial embedding in a given grid is NP-hard.Peer ReviewedPostprint (author's final draft

Drawing Trees with Perfect Angular Resolution and Polynomial Area

We study methods for drawing trees with perfect angular resolution, i.e., with angles at each node v equal to 2{\pi}/d(v). We show: 1. Any unordered tree has a crossing-free straight-line drawing with perfect angular resolution and polynomial area. 2. There are ordered trees that require exponential area for any crossing-free straight-line drawing having perfect angular resolution. 3. Any ordered tree has a crossing-free Lombardi-style drawing (where each edge is represented by a circular arc) with perfect angular resolution and polynomial area. Thus, our results explore what is achievable with straight-line drawings and what more is achievable with Lombardi-style drawings, with respect to drawings of trees with perfect angular resolution.Comment: 30 pages, 17 figure