The line planning problem in public transport deals with the construction of a system of lines that is both attractive for the passengers and of low costs for the operator. In general, the computed line system should be connected, i.e., for each two stations there have to be a path that is covered by the lines. This subproblem is a generalization of the well-known Steiner tree problem; we call ...

The advances in VLSI technology have led to complex and larger circuits. As the circuits become complex and large, the amount of time required for the design of such circuits increases. The people in the VLSI industry are looking for faster EDA (Electronic Design Automation) tools so as to reduce the design time. Routing is a phase in the design (physical design) of electronic circuits, wherein...

In the online Steiner tree problem, the input is a set of vertices that appear one-by-one, and we have to maintain a Steiner tree on the current set of vertices. The cost of the tree is the total length of edges in the tree, and we want this cost to be close to the cost of the optimal Steiner tree at all points in time. If we are allowed to only add edges, a tight bound of Θ(logn) on the compet...

Given an edge-weighted undirected graph G = (V,E, c, w), where each edge e ∈ E has a cost c(e) and a weight w(e), a set S ⊆ V of terminals and a positive constant D0, we seek a minimum cost Steiner tree where all terminals appear as leaves and its diameter is bounded by D0. Note that the diameter of a tree represents the maximum weight of path connecting two different leaves in the tree. Such p...

In this paper, we study a Steiner tree related problem called “Terminal Steiner Tree with Bounded Edge Length”: given a set of terminal points P in a plane, one is asked to find a Steiner tree T such that any point in P is a leaf in T and the length of each edge in T is no more than a constant b. The objective of the problem is to minimize the number of Steiner points in T . This problem is mot...

We construct an example of a Steiner tree with an infinite number of branching points connecting an uncountable set of points. Such a tree is proven to be the unique solution to a Steiner problem for the given set of points. As a byproduct we get the whole family of explicitly defined finite Steiner trees, which are unique connected solutions of the Steiner problem for some given finite sets of...

The Steiner tree problem asks for the shortest tree connecting a given set of terminal points in a metric space. We design new approximation algorithms for the Steiner tree problems using a novel technique of choosing Steiner points in dependence on the possible deviation from the optimal solutions. We achieve the best up to now approximation ratios of 1.644 in arbitrary metric and 1.267 in rec...

We investigate a practical variant of the well-known graph Steiner tree problem. In this variant, every target vertex is required to be a leaf vertex in the solution Steiner tree. We present hardness results for this variant as well as a polynomial time approximation algorithm with performance ratio ρ + 2, where ρ is the best-known approximation ratio for the graph Steiner tree problem.  2002 ...

The Steiner tree problem asks for the shortest tree connecting a given set of terminal points in a metric space. We design new approximation algorithms for the Steiner tree problems using a novel technique of choosing Steiner points in dependence on the possible deviation from the optimal solutions. We achieve the best up to now approximation ratios of 1.644 in arbitrary metric and 1.267 in rec...

For a metric graph G = (V,E) and R ⊂ V , the internal Steiner minimum tree problem asks for a minimum weight Steiner tree spanning R such that every vertex in R is not a leaf. This note shows a simple polynomial-time 2ρapproximation algorithm, in which ρ is the approximation ratio for the Steiner minimum tree problem. The result improves the approximation ratio 2ρ+ 1 in [3].